Preheat oven to 375 and prepare an 8×8 square pan by lining with parchment paper and spraying with cooking spray.
Make the crust by whisking together in a medium bowl the flour, brown sugar, baking soda, baking powder and salt. Add the melted butter. The dough will be crumbly but make sure all of the butter is incorporated.
Reserve 3/4 cup of the crust and press the remaining into the bottom of your 8×8 prepared baking pan.
For the sour cream filling, mix together in a large bowl the sour cream, sugar, 1 Tbsp flour, egg, and vanilla. Pour over the crust in your 8×8 pan.
In a medium sized bowl combine cinnamon and nutmeg. Coat the apples with the mixture and sprinkle apples evenly over sour cream mixture.
Sprinkle your reserved 3/4 cup crust over the top and bake for 25-28 minutes or until golden brown. Cool completely and serve into squares. Store in the refrigerator up to 3 days.