Cream together the butter and sugar, then mix in the eggs, vanilla, yogurt, and dry ingredients until combined.
Spread half the batter into a lined 8x8 baking pan until even.
Spread all but a few tablespoons of the brown sugar and cinnamon on top of the batter.
Spread the rest of the batter on top and then sprinkle the rest of the cinnamon sugar on top. Bake at 350 for 30 minutes.