Start by preheating the oven to 350F.
Combine in a large bowl, the cornmeal, flour, baking powder, salt, cayenne pepper, and brown sugar. Whisk until well combined.
Whisk together in a smaller bowl, the milk, and sour cream. Set aside.
Melt the butter. Coat a 8"x8" baking pan with non-stick spray and line the pan with parchment paper while the butter gets a chance to cool down.
Pour the milk mixture into the dry ingredients and gently fold together with a rubber spatula. While still lumpy, add the melted butter to the bowl. Stir until well combined, but still slightly lumpy.
Place the batter into the prepared 8"x8" pan and level the batter with a spatula. Bake in the preheated 350F oven for 25 minutes, or until a toothpick inserted in the middle comes out clean.
Remove the baked cornbread from the oven and let it cool for 5 minutes. Lift out the cornbread from the pan by the parchment paper. Cut the cornbread in your desired sized pieces and enjoy warm!