Preheat the oven to 350°F. :Liberally spray a non-stick 13 x 9-inch metal baking pan with cooking spray. Set aside.
In the bowl of a stand mixer cream together the butter, 1 cup sugar and powdered sugar with the vanilla. Beat for 2-3 minutes until light and fluffy. Scrape the sides of the bowl as needed.
Add the eggs one at a time beating well after each addition.
In a separate bowl sift together the flour, baking powder, cream of tarter, salt and nutmeg. Turn the mixer to low speed and gradually add to the mixer until all has been added. Increase the speed and beat until fully combined about 1 minute.
Spread the dough evenly into the pan.
Mix together the remaining ¼ cup sugar and cinnamon. Sprinkle over the top.
Bake for 25 minutes or until a toothpick inserted into the center shows moist crumbs.
Cool completely on a cooling rack. Store at room temperature tightly sealed.
When mixing the cinnamon sugar topping start with 2 tsp and taste. Use as is or, add more cinnamon to your personal preference.