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Rhubarb and Marzipan Upside Down Cake

yield: 1 nine-inch cake
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Special Equipment

  • A food processor
  • a 9 x 3-inch round cake pan or a 9-inch springform pan (see baker's notes)

Ingredients

For the Marzipan Crumble

  • 2.5 ounces marzipan
  • 1 tablespoon almond meal
  • 1 tablespoon cold unsalted butter
  • 1 1/2 teaspoons granulated sugar

For the Rhubarb Topping

  • 1 1/2 pounds rhubarb, rinsed and sliced into 1/2 inch cubes ((around 4 cups))
  • 2 teaspoons cornstarch
  • 1/4 cup dark brown sugar
  • 2 tablespoons unsalted butter

For the Vanilla Lemon Sponge Cake Base

  • 1 cup granulated sugar
  • zest of 1 lemon, freshly grated
  • 2 cups cake flour
  • 1 1/4 teaspoons kosher salt
  • 1 teaspoon ground ginger
  • 1 cup (2 sticks) unsalted butter, at room temperature
  • 4 large eggs
  • 1 teaspoon vanilla extract
  • 1/3 cup sour cream
  • 2 teaspoons lemon juice

Instructions

For the Marzipan Crumble

  • Break 2.5 ounces marzipan into small pieces and place in the bowl of a food processor. Pulse a few times, before adding 1 tablespoon almond meal through the feed tube, pulsing to blend. Continue pulsing and add 1 tablespoon cold butter and 1 1/2 teaspoon granulated sugar. DO NOT PROCESS FOR MORE THAN A FEW SECONDS AT A TIME — stop pulsing when the crumble is in pea-sized clusters.

For the Rhubarb Topping

  • Prepare a 9 x 3-inch round cake pan by spraying generously with cooking spray. Line the bottom with a parchment paper circle, before spraying generously with cooking spray as well. Place the cake pan on a rimmed baking sheet and set aside.
  • In a medium bowl, toss together 1 1/2 pounds sliced rhubarb cubes and 2 teaspoons cornstarch until well combined. Set aside.
  • In a saucepan over medium heat, combine 1/4 cup light brown sugar and 2 tablespoons unsalted butter. Whisk constantly until the mixture is smooth and bubbling, about 2 minutes.
  • Once the butter has fully melted and the mixture is combined, remove from heat. Set aside to cool on a wire rack for 5 minutes or so, before pouring into the bottom of the prepared cake pan.
  • Spoon the rhubarb and its juices on top of the brown-sugar mixture in the cake pan. Use your fingers to sprinkle the marzipan crumble on top of the fruit and brown-sugar mixture. Set aside while you make the cake base.

For the Vanilla Lemon Sponge Cake Base

  • Center a rack in the oven and preheat to 325 (F).
  • In a medium bowl, combine 1 cup granulated sugar and the zest from 1 freshly grated lemon. Use your fingers to rub the zest into the sugar — this will help release oils from the lemon zest and make the sugar aromatic. Set aside once the sugar starts to become fragrant.
  • In a medium bowl, whisk together 2 cups cake flour, 1 1/4 teaspoons kosher salt, and 1 teaspoon ground ginger until well combined. Set aside.
  • In the bowl of a freestanding electric mixer fitted with a paddle attachment, combine 1 cup granulated sugar and lemon zest (from the 1st step) and 1 cup unsalted butter. Beat on medium-high speed until the mixture is light and fluffy, at least 5 minutes, stopping to scrape down the bowl halfway through.
  • Once the mixture is light and fluffy, slow the mixer down to its lowest setting. Add 4 large eggs, one at a time, only adding the next egg after the previous one has been fully incorporated. Once all the eggs have been added, add 1 teaspoon vanilla extract and continue mixing until fully incorporated, before adding 1/3 cup sour cream and 2 teaspoons lemon juice. Continue mixing until fully incorporated, then stop the mixer and use a rubber spatula to scrape down the sides of the bowl.
  • Turn the mixer back to its lowest speed and add the flour mixture (from the 2nd step), 1/4 cup at a time, until just incorporated. It's okay to stop the mixer a little early if you have 1 or 2 flour streaks left, and finish the rest by hand using a rubber spatula.
  • Transfer the batter to the cake pan containing the brown sugar and rhubarb, spooning it over the fruit. Use an offset spatula to smooth out the top.
  • Transfer the baking sheet containing the cake pan to the preheated oven and bake for 1 hour and 15 minutes, or until the top of the cake bounces back when gently touched and a cake skewer inserted into the center of the cake comes out without any large, moist crumbs.
  • Place the pan on a wire rack and cool for 15 minutes. After 15 minutes, run a knife around the cake, place a plate on top of the pan, and turn it upside-down. Tap on the base of the cake pan until the cake releases onto the plate. Once the cake is on the plate, allow to cool on a wire rack. Serve while warm.