Preheat the oven to 450 degrees. In a large bowl, stir together the flour, baking powder, salt, baking soda, and 1 1/2 teaspoons of garlic powder. Use a pastry blender or your fingertips to work the butter into the flour mixture until it resembles coarse crumbs.
Stir the cheddar into the mixture than stir in the buttermilk (start with 3/4 cup of the buttermilk and then gradually add more until it all comes together).
Scoop 1/4-cup size scoops of the dough onto a baking sheet with the edges of each biscuit barely touching. Bake until golden, 12-15 minutes.
In a small bowl, stir together the melted butter and remaining garlic powder. Brush the tops of the biscuits liberally