1 cup (8 ounces) unsalted butter, at room temperature
1 whole egg plus one yolk
1 tablespoon vanilla extract
For the topping:
2 tablespoons granulated sugar
2 teaspoons cinnamon
Instructions
Preheat the oven to 350 degrees F. Grease a 9×13-inch baking pan; set aside.
Whisk together the flour, baking powder, salt, and cinnamon in a medium bowl; set aside.
Beat together the butter and brown sugar on medium speed until light and fluffy, about 5 minutes. Add the eggs one at a time, and then the vanilla. Beat until smooth.
On low speed, gradually add the dry ingredients until just combined. Use a spatula to give the dough one last stir making sure there are no streaky bits.
Use a greased spatula to help spread the dough into the prepared pan. (Or your hands!) Combine the granulated sugar and cinnamon in a small bowl and sprinkle evenly over the top of the batter.
Bake for 25-30 minutes or until the surface springs back when gently pressed. Cool completely before cutting. Store in an airtight container at room temperature.