Cake for breakfast? Um yes, please! This delicate, crumbly treat is as delicious to look at as it is to taste.
1. Melt 4 tbsp. of butter in a small bowl. Add the flour, sugar, lemon juice and zest. Mix with a fork to combine. Set aside.
2. Preheat oven to 325 degrees. Invert the bottom of an 8-inch springform pan (to make it easier to slide the cake off the bottom), then lock on the sides of the pan. Grease and flour the bottom and sides of the pan. Set aside.
3. In a small bowl, combine the flour, salt, and baking powder. Set aside.
4. In the bowl of a stand mixer fitted with the paddle attachment, combine the butter, lemon zest, and sugar. Beat for several minutes until light and fluffy, scraping down the sides of the bowl as needed.
5. Beat in the egg and vanilla bean paste until just blended.
6. In a measuring cup (preferably with a spout) combine buttermilk and lemon juice. Add a third of the buttermilk mixture and half of the flour mixture to the creamed butter and sugar. Beat on low until incorporated. Repeat until both the buttermilk and flour mixtures are incorporated.
7. Pour batter into the prepared pan and spread evenly. Sprinkle with the crumble topping (leaving some in large clumps) and bake for 40 minutes, or until the top is lightly browned and a toothpick inserted in the center comes out almost clean.
8. Cool the cake on a wire rack. Let cool completely before removing springform sides. Carefully slide cake onto a serving plate and dust with powdered sugar.
9. Dollop with lemon curd whipped cream if desired.