Preheat the oven to 375 degrees. In a large bowl, combine the ground beef, breadcrumbs, egg, diced onion, salt, and black pepper. Mix just until the ingredients come together.

Press half the meat mixture into a loaf pan to form a base. Spread the shredded cheddar cheese evenly across the center, then top with the remaining meat mixture and seal the edges.

Stir the ketchup and brown sugar together in a small bowl. Spread half the sauce over the top of the meatloaf.

Bake the meatloaf for 45 minutes until it reaches an internal temperature of 160 degrees.

While the meatloaf bakes, mix the flour, baking powder, and salt in a bowl. Cut in the cold butter until the mixture looks like coarse crumbs. Pour in the buttermilk and stir until a soft dough forms.

Turn the dough onto a floured surface, pat it to 1 inch thick, and cut out biscuits. Place them on a baking sheet and bake for 12 to 15 minutes until golden.

Let the meatloaf rest for 5 minutes, then slice and serve with the remaining sauce and warm biscuits.