8 Tablespoons (1 stick) unsalted butter, melted, plus more for the pan
1 cup all-purpose flour, plus more for the pan
2 teaspoons baking powder
1/2 cup sugar
1/2 teaspoon salt
1 large egg
1 teaspoon vanilla extract
1/2 cup whole milk
1/4 cup sour cream
Rhubarb Compote (Recipe follows)
Whipped cream for serving
Preheat the oven to 400 degrees F. Coat a 10-inch ovenproof skillet, preferably cast iron, with butter and flour, shaiking out any excess flour.
In a medium bowl, combine the flour, baking powder, sugar, and salt. In a large bowl, whisk together the egg, vanilla, milk, sour cream, and melted butter. Gently stir the wet ingredients into the dry until just incorporated.
Pour about two-thirds of the compote into the greased skillet and spread evely. Pour the cake batter over it, spread evenly, then dollop the remaining compote over the top. Use a butter knife to swirl together the batter and compote.
Bake until a cake tester or knife inserted in the middle of the cake comes out clean, about 25 minutes. I like to serve this warm, directly from the skillet, with a big spoon and a bowl of whipped cream to dollop on top.
RHUBARB COMPOTE
3 cups chopped rhubarb (1-inch pieces)
2/3 cup sugar
1 teaspoon grated lemon zest
2 teaspoons fresh lemon juice
2 teaspoons cornstarch
In a medium heavy-bottomed saucepan, combine the rhubarb, sugar, lemon zest, lemon juice, and cornstarch. Bring to a simmer over medium heat, stirring constantly until the rhubarb becomes tender and sauce-like, about 5 minutes. (Mine took longer). Remove from the heat and allow to cool to room temperature. This will keep in the fridge for up to a week.