Warm Cream-Cheese Snickerdoodle Tart

5 ounces cream cheese, at room temperature
3 ounces mascarpone cheese, at room temperature
1/2 cup unsalted butter, at room temperature
1/2 cup granulate sugar
2 large eggs
1/4 tsp freshly grated nutmeg
1/4 tsp cream of tarter
1 tsp vanilla extract
1/2 tsp cinnamon
1 baked Pastry Tart Shell (recipe follows)
cinnamon sugar

Preheat oven to 350F.
In the work bowl of an electric mixer, combine cream cheese, mascarpone cheese, sugar, and butter. Beat on high speed until light and fluffy, about 3 minutes.
Add eggs, one at a time, scraping down the bowl after each addition. Add vanilla and beat until incorporated and smooth. Add the nutmeg, cinnamon and cream of tarter and beat until fully incorporated.
Spread filling evenly in prepared tart shell.
Bake for 20-25 minutes, or until center is set and edges are light golden. Remove pan from the oven and allow tart to stand for two minutes. Sprinkle with cinnamon sugar.
Serve warm. (I ate it both ways and enjoyed it either warm or chilled)

Pastry Tart Shell

Makes 1 (10 1/2-inch) tart shell

1 1/3 cup all-purpose flour
pinch of salt
1/2 tsp cream of tarter
1/4 tsp freshly grated nutmeg
1/2 cup unsalted butter, cut into cubes and chilled
1/2 cup plus 2 TBSP powdered sugar
2 egg yolks
cinnamon sugar

Using a food processor, combine the flour, cream of tarter, nutmeg, and salt and pulse to mix. Add butter and pulse until mixture resembles coarse bread crumbs.
Add sugar and egg yolks and pulse again, just until the mixture comes together and pulls aways from the sides of the bowl.
Transfer dough to a sheet of plastic wrap. Form into a disc ans wrap in plastic. Refrigerate for at least 1 hours or overnight.
Prepare fluted tart pan by buttering pan and then sprinkling cinnamon sugar into the pan. Get both the bottom and sides of the pan.
Roll pastry out on a lightly floured surface into a circle. Fit dough into prepared tart pan, pressing evenly over the bottom and up the sides. Line tart shell with parchment paper and fill with dried beans or pie weights.
Bake tart shell for 20 minutes (at 350F), or until edges are very light brown. Remove parchment paper and weights.
Bake tart shell for 5-10 minutes more, or until lightly golden throughout.. Cool on a rack before filling.