In the bowl of a stand mixer fitted with a paddle attachment, cream together the butter and sugar until they're light, fluffy, and thoroughly combined; about 2-3 minutes.
While the butter and sugar are creaming together, in a separate bowl whisk together the flour, baking powder, baking soda, cornstarch, and salt. Set aside.
In the stand mixer butter/sugar mixture, add in the egg, sour cream, vanilla, and almond extract and mix until combined.
Add in the flour and mix on low speed until just combined. Create a circle-shaped disc with the dough, wrap in plastic wrap, then place into the fridge for at least an hour.
Preheat the oven to 375 degrees and prep a cookie sheet with a sheet of parchment paper, set aside.
Roll out the dough onto a lightly floured surface or sheet of parchment paper. Cut out 2-3" inch cookies with a cookie cutter and place the circles onto the prepared parchment sheet about 3 inches apart.
Bake for 7-8 minutes (they should still be pale and not golden around the edges), then transfer the cookies to a cooling rack to cool completely.