Heat the oven to 375°F and grease a 2-quart baking dish. Brown beef, onion and pepper in a skillet for 8 minutes until the beef reaches 160°F; drain excess fat.
Stir in ketchup, tomato paste, water, vinegar, brown sugar, Worcestershire, filling salt and pepper. Simmer for 8 to 10 minutes until thick, then spread the hot filling in the baking dish.
Whisk cornmeal, flour, granulated sugar, baking powder and cornbread salt in a bowl. In another bowl, whisk milk, egg and oil.
Stir the wet ingredients into the dry just until combined. Spoon the batter over the hot filling and spread gently to cover most of the surface.
Bake for 22 to 27 minutes until the cornbread is golden and a tester inserted into the bread comes out without wet batter. Rest for 10 minutes before serving both layers together.