Crumb Cake

Ingredients

• 1 cup + 2 Tbsp all-purpose flour
• 1/3 cup packed light brown sugar
• 1/3 cup granulated sugar
• 1 tsp ground cinnamon
• 1/4 tsp salt
• 1/2 cup unsalted butter, melted
• 1 cup all-purpose flour
• 3/4 tsp baking powder
• 1/8 tsp baking soda
• 5 Tbsp unsalted butter, softened
• 1/2 cup granulated sugar
• 1 large egg
• 1 tsp vanilla extract
• 1/4 cup milk
• 1/4 cup sour cream

Directions

1. Heat the oven to 350 degrees. Butter an 8 by 8-inch baking dish, fit it with 2 sheets of parchment, and butter the parchment as well; if you are not planning to lift the cake out in one piece, you can butter the dish and dust it lightly with flour instead.
2. For the crumbs, combine the brown sugar, granulated sugar, cinnamon and salt in a mixing bowl with a whisk. Add the melted butter and stir until everything is moistened. Gradually work in the flour with a wooden spoon or a spatula until no dry flour is visible, then let the mixture sit while you move on to the batter.
3. For the cake, whisk the flour, baking powder, baking soda and salt in a mixing bowl for 20 seconds, then set that bowl aside. In the bowl of an electric stand mixer fitted with the paddle attachment, beat the butter and granulated sugar until the mixture looks pale and fluffy. Mix in the egg and vanilla. In the liquid measuring cup you used for the milk, whisk the sour cream together with the milk.
4. Add 1/3 of the flour mixture to the butter mixture and mix only until it comes together, then pour in 1/2 of the milk mixture and mix just until blended. Repeat that alternating pattern once more, then finish with the final 1/3 of the flour mixture, mixing until it is almost incorporated. Scrape the sides and bottom of the bowl with a rubber spatula, then fold the batter until it is fully combined.
5. Pour the batter into the prepared baking dish and spread it into an even layer. Break the crumb mixture into pea size bits and scatter them evenly across the batter.
6. Bake until a toothpick inserted in the center comes out without wet batter and the cake does not sink when you gently touch the middle, about 32 – 35 minutes. Let the cake cool in the pan for 10 minutes, then use the parchment overhang to lift it out and transfer it to a wire rack to finish cooling. Store in an airtight container.