Open Sesame: Rye Rhubarb Tahini Tart

GAH, I love this season for baking. (Okay, there isn’t really a season that I don’t like, but bear with me.) Finally the rhubarb and cherries are here, and gorgeous berries are signaling the imminent arrival of summer. I’m still fairly new to rhubarb, having only discovered it a few years ago, and every year I’ve been delighted to find new and creative ways to use it. I’ve also been using a lot of tahini (pure sesame paste) in various sweet and savory applications, and I stopped dead in my tracks when I saw a rhubarb-frangipane freeform tart from Seed + Mill (one of my favorite spots in NYC) on feedfeed that combined both rhubarb and tahini in one dessert. I mean… what? Like, who was the genius who first put those two ingredients together and thought it would be a good idea? I want to be you. I recently posted this Double Sesame Banana Bread, which was another lovely tahini-baking revelation, but this was totally next-level stuff. Frangipane is an almond/butter/egg mixture that results in a puffy, nutty filling often used in almond croissants, tarts, and various other pastries. The source recipe swapped out the butter for tahini, and it worked perfectly; like I said, genius. The rhubarb and frangipane are wrapped up in pie crust pastry and baked as a rustic tart. Only… I wanted to change up a little something. I thought back to one of my favorite-ever fruit desserts (okay, rhubarb is technically a vegetable), last year’s Rye & Rhubarb Upside-Down Cake, and immediately grabbed my copy of Good to the Grain, which I knew had a rye pie crust recipe. Rye and rhubarb proved to be a pretty magical combination, so I knew that that would be the perfect crust to deploy in this rhubarb-tahini situation.

This rye pastry dough is positively lovvvvvely– not just here, but for pretty much any fruit tart, and probably a lot of other things that I haven’t thought of yet, but will undoubtedly get very excited about in the future. On another positive note, the dough is very easy to work with throughout the making and shaping process. It takes a little more work than a typical pie crust, and you are perfectly welcome to use your favorite pie dough recipe instead, but I urge you to give this a try, despite the extra steps. You will pull together the ingredients with your hands, then employ a second phase of preparation: folding the dough like laminated pastry. It’s akin to a “rough puff” dough, i.e. shortcut puff pastry, but with the slight tangy/nutty edge of the rye flour. This is a great technique to have in a baker’s back pocket.

The first time I made the recipe, I decided to make mini-tarts just to try my own spin on it. They came out okay, but I felt that there was a lot of room for improvement. I was disappointed that the rhubarb pieces did not retain their pink color that well, the dough looked a little anemic, and by the time I photographed them in daylight the following morning, they just looked sad and soggy. However, they were still delicious, and I knew that it was worth another shot. There is a complex web of scrumptious flavors here, what with the tart rhubarb, nutty tahini-almond frangipane, and nutty/tangy rye pastry. It straddles the line of sweet and savory, and I wanted to push it just a tad more to the sweet side.

For my second attempt, I made a single large rectangular tart like the original recipe, which was a lot less fussy than small ones. The first time, I had sprinkled brown sugar sparingly over the rhubarb, but I used a more liberal amount this time to offset the tart/savory flavor, and I sprinkled the crust with Demerara sugar. Despite these sweetening measures, it turned out that this particular batch of rhubarb was more sour than the first batch, so I had to serve the tart with ice cream and strawberries. It was terrible. 😉

Tips for success with this recipe:

• If the dough gets warm and melty, stick it in the fridge to firm up.
• If you get melty butter spots in the dough while rolling it out, pat a little flour over them to “patch” those areas and keep working.
• Use a bench scraper to shape the dough edges as you roll it out. You can trim uneven pieces and patch corners and edges if needed.
• The dough seems to be very forgiving– it is supposed to be dry-ish and crumbly in the first stage like “rough puff”, but it was more cohesive than expected. The second time I made it, it was way too wet, so I added a little flour against the recipe’s advice. (I adjusted the water quantity, which is reflected below.) It turned out flaky and delicate both times, and the second time it even sat in the fridge assembled (pre-baking) all night without turning soggy on the bottom!
• Feel free to cut the rhubarb into any shapes you want. I liked the herringbone pattern in the original recipe, so I stuck with that, but you can do whatever you like: long pieces, basketweave, randomly arranged pieces, etc.
  • If you make the herringbone pattern, shorten the edges of the end pieces in order to get the same shape on both sides of the tart– the shape of the bias-cut pieces is more pointed on one side. As you can see, one side of mine turned out more rounded on the corners, whereas the other side had pointier corners. Not a huge deal, but if you want the tart to be somewhat symmetrical, it’s helpful to trim the rhubarb.
• Field rhubarb is more green and loses some of its pink color when baking, whereas hothouse rhubarb tends to be deep red and holds on to its color. I found hothouse rhubarb to be more tart, but that might have just been random. You can use either– I used field-grown for the first batch of tarts and hothouse for the second, large tart.
• You can make a single large rectangle or circle, or 6 small tarts, or really whatever size you want. When I made the mini ones, I found it hard to form uniform dough circles (but I’m dough-shaping-challenged), though rounded squares worked fine since these are roughly shaped tarts anyway.
• Make sure to leave enough dough on the border to pull it up and over the edges of the rhubarb pieces without tearing, about 1½”, so that the shape doesn’t unravel in the oven.
• Bake the tart cold, as it will help keep its shape.
• This tart is best within a few hours of baking (eat it warm!) and gets soggy on the second day. You can assemble it in the evening and bake in the morning if you plan to serve it the next day– simply wrap it tightly in plastic wrap and store it in the fridge overnight.

This is a gorgeous spring dessert for any occasion. The flavors and textures are interesting, creative, aaaaand freaking delicious. I love the flakiness of the rye pastry, the sweet and sour flavor of the fillings, and I love how the tahini frangipane puffs up around the rhubarb. It’s a keeper. 😀

Rye Rhubarb Tahini Tart
Adapted from Seed + Mill & Good to the Grain by Kim Boyce
Yields 10-16 servings

If your rhubarb is especially tart, strawberries and ice cream are a nice foil. Also, I only used half of the filling called for in the original recipe, which is reflected here. Feel free to increase the quantity if you want a thicker frangipane layer.

For the rye pastry dough:

• 1 cup (120g) all-purpose flour
• 1 cup (120g) dark rye flour
• 1 tablespoon granulated sugar
• 1 teaspoon kosher salt
• 6 ounces (1½ sticks/12 tablespoons) cold unsalted butter, cut into ½” pieces
• 1 teaspoon apple cider vinegar
• 6-8 tablespoons ice water

For the tahini frangipane:

• ¼ cup (35g) raw almonds
• 3 tablespoons (37g) granulated sugar
• 1½ tablespoons all-purpose flour
• 1 egg
• ½ teaspoon pure vanilla extract
• 3 tablespoons (30g) pure tahini (sesame paste)
• 1 tablespoon maple syrup (optional)

For the filling & assembly:

• 6-7 stalks (about 600g) rhubarb, trimmed of leaves and ends, cut into pieces of your choice
• 1 tablespoon light brown sugar
• 1 beaten egg or 1 tablespoon milk (egg will yield a shinier, more golden crust)
• 2 tablespoons Demerara or Turbinado sugar
• Toasted sesame seeds for sprinkling

For serving (optional):

• Confectioners’ sugar
• Vanilla or strawberry ice cream (I used Jeni’s Splendid Ice Cream Brambleberry Crisp)
• Sliced strawberries

To make the rye pastry dough:
Sift together the all-purpose and rye flours, sugar, and salt into a large bowl; add back in any large grains that got caught in the sifter. Add the cold butter pieces and work them into the flour mixture with your hands, rubbing the cubes into smaller bits and coating the flour. The largest pieces should be about the size of a hazelnut– you do want to maintain some butter chunks. Work quickly so the butter doesn’t get too soft.

Add the apple cider vinegar and 6 tablespoons of ice water, and work the liquid into the mixture with your hands, starting from the outside and working toward the center. Use a light hand here, and only mix until the dough is just moistened. If dry, add more water 1 tablespoon at a time (up to 2 extra tablespoons) and blend it in with your hands. The dough should hold together in a rough lump with some ragged pieces. If it’s too wet, knead in a couple of tablespoons of flour so it’s no longer sticky. Form the dough into a rough ball, then flatten and shape it into a square. Sprinkle a few drops of water on top and wrap the dough tightly in plastic wrap. Chill it for at least 1 hour in the fridge or overnight.

The second stage involves folding the dough in a similar way as puff pastry. Roll the dough with a rolling pin into a rectangle about 8×11″. The dough should still look pretty rough and crumbly at this point; just bring it together with your hands and a bench scraper if you have stray pieces. Carefully take the short side on the left and fold it over the middle ⅓ of the dough, then fold the right side over it, so that the dough looks like a folded letter. Rotate the dough 90° so that the seam of the dough faces the top of the cutting board (away from you). This is called the first “turn”. Repeat the rolling (8×11″), folding, and rotation twice more, for a total of 3 turns. The dough will smooth out more with each turn. Wrap the dough tightly in plastic wrap and chill for at least 1 hour or up to 3 days.

To make the tahini frangipane:
Place the almonds in a small food processor (or blender) and pulse them until they’re broken down into a fine meal. Add the sugar and flour and pulse until blended; then add the eggs and vanilla and pulse, followed by the tahini. The mixture will thicken considerably when you add the tahini– you’re looking for a wet paste consistency. If the mixture is very dry/sticky, add a tablespoon of maple syrup to loosen it. (I did not need to do this.)

I made the full recipe of frangipane, which is why you see two eggs here. Feel free to do this if you want more of it; otherwise you’ll only use 1 egg.

To assemble the tart:
Line a baking sheet with parchment paper. Take the dough packet out of the fridge, unwrap, and roll out the pastry in your desired shape/size on a lightly floured surface. A single large rectangle (about 16×12″) worked best for me, though you can also cut it in half for two smaller tarts, or cut it into 4-6 pieces for mini ones.  Transfer the rolled-out dough to the prepared sheet pan. Spread the frangipane mix over the pastry with a small offset spatula, leaving a 1½” border all the way around.

Arrange the rhubarb pieces over the frangipane in a single layer (in an artistic pattern if you wish). Fold the dough border up and over the edge of the rhubarb, folding and pinching the dough together in various spots to secure the rhubarb and make it rustic-looking. If you are baking the tart on the same day, put the sheet pan in the fridge for 30-45 minutes, or until the dough has firmed up. In the meantime, preheat an oven to 350°F and position a rack in the center of the oven.

If you plan to bake the tart the next day, wrap the whole sheet pan with plastic wrap and store it in the fridge overnight. (You might want to place another sheet of parchment over the surface of the tart as a barrier from condensation.) Preheat the oven about 30 minutes before you plan to bake.

When ready to bake, retrieve the tart from the fridge and sprinkle the brown sugar evenly over the rhubarb. Brush the dough border with the beaten egg and sprinkle the Demerara or Turbinado sugar liberally over the wet egg. Sprinkle the toasted sesame seeds over both the dough and the rhubarb.

Bake the tart for 40-50 minutes (mine took 48 minutes), or until the pastry turns a handsome golden brown. Remove the pan and set it over a metal cooling rack for about 30 minutes, then slide the pan out from under the parchment paper and allow the tart to cool completely, or serve it warm. You can sprinkle it with some confectioners sugar if you wish, and/or serve with vanilla ice cream and sliced strawberries. It is best eaten the day it’s baked.

© Dafna Adler & Stellina Sweets, 2017.