The rhubarb was soft and sour/sweet, the rye flour gave a nice heft and chew to the crumb. There's lots of thoughtful touches in this recipe - from the very talented Yossy Arefi of Apartment 2B Baking Co - the addition of lemon zest to the fruit topping, the use of buttermilk to enrich the rye, a double dose of vanilla with bean and extract... Trust me, it's good. An upside-down cake to make life feel right way up again.
Rhubarb upside-down cake
Adapted from a recipe in Yossy Arefi's book Sweeter off the Vine, as published on Design*Sponge
This is good just as it is, but it's REALLY good with a big fat dollop of cream. If you don't have any buttermilk in the fridge, you can make your own by adding one and a half tablespoons of white vinegar or lemon juice to one and a half cups of milk (and letting it sit for five minutes to curdle).
1 pound (450g) rhubarb, leaves removed, cut into 2-inch (5cm) lengths
1 vanilla bean
3⁄4 cup (150g) sugar
1⁄4 cup (55g) unsalted butter
1 teaspoon lemon zest
1 cup (125g) plain flour
1 cup (130g) rye flour
1 tablespoon baking powder
1⁄2 teaspoon bicarb (baking) soda
1⁄2 teaspoon salt
1⁄2 cup (115g) unsalted butter, softened
1⁄2 cup (100g) sugar
2 large eggs, at room temperature
1 teaspoon vanilla extract
1 1⁄2 cups (355ml) buttermilk, at room temperature
Position a rack in the centre of the oven and preheat to 375F (190C). Butter a 9-inch cake pan or springform pan, 3 inches tall, line it with parchment paper, and butter that too. Dust the pan and paper with flour.
To make the rhubarb topping: Use the tip of a knife to split the vanilla bean lengthwise and scrape out the seeds; reserve the pod for another use. Combine the sugar, butter, vanilla seeds, lemon zest, and salt in a skillet and set over medium low heat. Heat, stirring occasionally, until the sugar and butter begin to melt together, then add the rhubarb. Cook the rhubarb, turning it occasionally in the pan, until it is juicy, tender, and slightly caramelized but not falling apart, 6 to 8 minutes. Pour the rhubarb and its juices into the prepared pan and spread in an even layer. Set aside while you prepare the cake batter.
To make the cake: In a medium bowl, whisk the plain and rye flours, baking powder, bicarb soda, and salt together. In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugar together at medium high speed until light and fluffy, about 5 minutes. Add the eggs, one at a time, mixing for 30 seconds after each addition. Add the vanilla and mix for 30 seconds. Use a rubber spatula to scrape down the sides and bottom of the bowl. Alternate adding the flour mixture and the buttermilk in three additions and mix until just combined. Carefully pour the batter over the rhubarb in the pan and smooth the top. Tap the pan gently on the counter to remove any air bubbles. If using a springform pan, set it on a baking sheet to catch any potential leakage.
Bake the cake until the top is golden and a toothpick or skewer inserted into the center comes out clean, 30 to 35 minutes. Let the cake cool on a rack for 15 minutes, then carefully invert onto a serving platter. Remove the parchment paper and reposition any rhubarb that has stuck to the paper. Cut into wedges and serve warm.