1 1/4 cups confectioners' sugar, plus more for dusting
1/2 teaspoon pure vanilla extract
4 large egg yolks
2 large eggs
1/4 cup sour cream
Preheat the oven to 350°. Butter and flour an 8-inch round cake pan. In a medium bowl, whisk the cornmeal with the cake flour and baking powder.
In a food processor, combine the softened butter and almond paste and process until very smooth. Add the 1 1/4 cups of confectioners' sugar and the vanilla extract, and process until light and fluffy. With the machine on, add the egg yolks and whole eggs, 1 at a time, processing in between additions, until smooth. Add the sour cream and process until fully blended. Scrape the batter into a large bowl and stir in the dry ingredients.
Scrape the batter into the prepared cake pan and smooth the surface. Bake in the lower third of the oven for about 35 minutes, or until the cake is golden, puffy and pulls away from the side of the pan. Transfer the cake to a wire rack and let it cool in the pan for about 10 minutes. Invert the cake onto the rack and let it cool completely. Turn the cake right-side up and sift confectioners' sugar over the top before serving.
The cake can be stored in an airtight container at room temperature for up to 4 days, or refrigerated for up to 1 week.