rhubarb crumble cake with strawberry jam swirl

Rhubarb Crumble Cake with Strawberry Jam Swirl
Makes one 9-inch cake

Inspired by Nigella Lawson via The New York Times

For the rhubarb:
3 stalks (about 215 grams) rhubarb, trimmed and chopped into 1/2-inch pieces
1/4 cup (55 grams) brown sugar
juice of one lemon
1/2 vanilla bean, seeds scraped

For the cake:
2 cups + 2 tablespoons (270 grams) flour
3/4 cup (155 grams) sugar
1 teaspoon (4 grams) baking powder
1/2 teaspoon (2 grams) baking soda
1/2 teaspoon (2 grams) salt
1 1/2 sticks (12 tablespoons or 170 grams) butter, cold and cut into 1/2-inch cubes
1 tablespoon (8 grams) oats
1 tablespoon (20 grams) brown sugar
1 cup (236 ml) buttermilk
1 egg
1 tablespoon (15 ml) vanilla
1/2 cup (170 grams) strawberry jam

Preheat oven to 375. Butter and flour a 9-inch springform pan and set aside.

In a small bowl mix rhubarb (it should measure about 1 1/2 cups chopped), brown sugar, lemon juice and vanilla bean seeds. I just tossed in the pod – because why not?! – and let the whole thing chill out while you are making the cake. Cook the strawberry jam over low heat in a small saucepan so that it loosens and just begins to bubble. Turn off the heat and let it hang out as well.

In a large bowl whisk together flour, sugar, baking powder, baking soda, and salt. Add the butter, toss each piece so it is coated in flour and begin to work the butter in by hand until the mixture resembles coarse crumbs. Scoop out about 1/2 cup (75 grams) into a small bowl and add oats and brown sugar. Press together until large crumbs form and refrigerate until you are ready to use.

Measure buttermilk into a liquid measuring cup (or a small bowl but who likes extra dishes to wash) and then whisk in the egg and vanilla. Add buttermilk mixture to the remaining flour mixture and combine using several quick strokes. Add in the rhubarb pieces – leaving any remaining juices and the vanilla bean behind in the bowl – and stir to fold in the bits.

Pour half the batter into the prepared pan then add the jam and spread it in an even layer leaving about 1/2-inch border on all sides. Add the remaining batter and smooth the top. Sprinkle crumble evenly over the top of the cake and bake for 35-40 minutes or until a tester comes out clean.

Let cool completely and serve.