Snickerdoodle Blondies

I saw this recipe on the blog, Culinary Concoctions by Peabody, and she made it look so delicious that I knew I had to try it. I made the blondies for Nick's Valentine's Day treat. He really liked them- so much that he had one for dessert and then again for breakfast the next morning! (I loved them too, but not for breakfast...) And he says this is a treat that he won't be taking to work because he wants to eat the entire pan himself.

8 ounces (two sticks) unsalted butter, at room temperature
1 cup granulated sugar
1 cup loosely packed light brown sugar
3 ounces Mascarpone cheese (I just used cream cheese because it is cheaper- not sure what the difference with Mascarpone would be)
2 eggs
1 tsp vanilla extract
½ tsp baking powder
1 tsp baking soda
pinch of salt
¾ tsp cream of tarter
¼ tsp freshly grated nutmeg
2 cups all-purpose flour

Cinnamon Sugar for coating (about 1/3 cup)- (I used 1/3 cup sugar and 4tsps cinnamon)

Preheat oven to 350F.
Butter a 9 by 13-inch pan. Sprinkle cinnamon sugar and move pan around to make sure that the bottom and sides are coated. Set aside.
In a medium bowl, sift together the flour, baking powder, baking soda, salt, nutmeg, and cream of tarter.
Using an stand mixer, cream together the butter and sugars. Beat for three minutes. Scrape down the bowl.
Add the Mascarpone cheese and beat until fully incorporated.
Add eggs, one at a time, scraping down the bowl after each addition.
Add the vanilla and beat for another 30 seconds.
On low speed add the sifted flour mixture. Mix until fully incorporated.
Spread mixture evenly into prepared pan. This will be hard as it is a thick batter. I found it easiest to just wet my hands a little and press the batter into the pan. Then even it out afterwards with a spatula.
Sprinkle more cinnamon sugar on top of the batter.
Bake for 20-25 minutes.