Preheat your oven to 475°F. Line a half-sheet pan with parchment paper.
In a large mixing bowl, whisk together flour, baking powder, baking soda, sugar, salt, garlic powder, cayenne, and Old Bay Seasoning. Stir in the cheddar cheese.
In a small mixing bowl, combine the buttermilk and melted butter. The butter will harden as it cools from being combined with the buttermilk. Add the wet ingredients to the dry ingredients, gently folding the two together with a rubber spatula. Mix until just combined.
Scoop out the dough in 1/4-cup portions, adding each biscuit to the parchment-lined half-sheet pan. Leave 1 inch between each biscuit. Bake until golden brown, about 12 minutes.
While the biscuits bake, whisk together the remaining melted butter, garlic powder, Old Bay Seasoning, and parsley. Brush the baked biscuits with the butter topping, and serve warm.