Ingredients:

• 1 Tablespoon flour, for coating the pan
• 2 cups all-purpose flour (measured correctly)
• 1 cup + 2 Tablespoons granulated sugar
• 1 teaspoon salt
• 10 Tablespoons (1 and 1/4 stick) unsalted butter, firm and cold
• 1 teaspoon baking powder
• 1/2 teaspoon baking soda
• 3/4 cup buttermilk, at room temperature¹
• 1 large egg, at room temperature²
• 2 teaspoons vanilla extract
• 2/3 cup packed light or dark brown sugar
• 2 teaspoons ground cinnamon

Directions:

1. Preheat oven to 350F. Generously spray a 9-inch springform pan³ with cooking spray or grease with butter. Sprinkle the bottom of the pan with 1 Tablespoon of flour and tap out the excess.
2. Whisk the flour, sugar, and salt together in a large mixing bowl until combined. Cut in the butter in very small pieces using a pastry blender or mix with a fork until the mixture resembles coarse crumbs. Set aside 1 cup of the butter/flour mixture.
3. Mix the baking powder and baking soda into the remaining flour mixture. Add the room temperature buttermilk, egg, and vanilla – you may want to do this with a mixer. The batter is very, very thick. Vigorously mix everything together until the batter is smooth, fluffy, and resembles frosting – about 2 full minutes. Spoon the batter into the prepared springform pan, smoothing the top.
4. Add the brown sugar and cinnamon to the reserved flour mixture. Toss with a fork until well blended. Sprinkle the crumbs over the batter, pressingly lightly so they stick. Bake the cake until the center is firm and a toothpick inserted in the center comes out clean – 50-58 minutes. Mine took 55 minutes. Allow to cool for 10 minutes, then remove the sides of the springform pan and allow cake to cool completely before serving (about 2 hours).
5. Make ahead tip: Cake tastes best on day 1 or day 2. The cake may be made 1 day in advance. Store covered at room temperature for up to 1 week. Cake can be frozen up to 2 months. Thaw overnight in the refrigerator.