Preheat the oven to 450 degrees F. Spray a baking sheet with nonstick spray or line with parchment paper and set aside.
Whisk together flour, baking powder, pepper, sugar, garlic powder, baking soda and cayenne pepper in a large mixing bowl. Add the cheese and toss to coat.
Whisk together the buttermilk and mayonnaise in a separate bowl.
Make a well in the center of the dry ingredients and add the wet ingredients. Stir until the flour is moistened, then fold in the pimentos.
Use a 2 tablespoon cookie scoop and drop onto the baking sheet, spacing them about 1 inch apart.
Brush the tops with melted butter. Sprinkle with flaky salt and additional black pepper if desired.
Bake until the tops are golden brown, 9 to 11 minutes