Ingredients
Method
- Heat the oven to 350F and line a 9x9 pan with parchment.
- Whisk the flour, cream of tartar, baking soda, and salt together.
- Stir the melted butter and brown sugar, then beat in the eggs and vanilla.
- Fold in the dry ingredients until just combined and spread into the pan.
- Sprinkle the cinnamon-sugar topping evenly across the batter.
- Bake 22 to 25 minutes until the top is set and the center is just firm, then cool before slicing.
Notes
Brown the butter first for a deeper, nuttier flavor.
