Preheat oven to 350 and spray an 8 inch cake pan (I used a springform) with cooking spray.
Put the flour, sugar and cinnamon in a food processor and pulse a few times to combine. Add the butter and pulse until the mixture looks like sand. Scoop out 1/3 cup and set aside.
Transfer the flour mixture to a mixing bowl and add the baking powder, baking soda, buttermilk, vanilla and egg and mix until combined.
Transfer the batter to your cake pan and smooth out the top to the edges of the pan with a spatula. Sprinkle on the saved 1/3 cup of the flour mixture.
Bake until toothpick inserted in the center comes out clean, about 30 minutes. Cool, cut into wedges and serve (maybe with a scoop of ice cream on top?)
Notes
Buttermilk: Buttermilk is fermented dairy product with a tangy, slightly sour flavor and a thicker consistency than regular milk. It adds both moisture and texture to this cake (and if you have leftover buttermilk, make these buttermilk cornmeal pancakes!).
Brown Sugar: Either light or dark brown sugar will work for this recipe.