Heat oven to 350^. Rub a 2 1/2 quart casserole dish with 1 Tablespoon of the butter; set aside. Put 1 quart of water and 2 teaspoons salt into a medium pot; bring to a boil. Gradually add cornmeal while whisking vigorously. Reduce heat to low and cook, stirring often, until thick about 9 minutes. Add remaining 3 Tablespoons butter and stir until combined. Spoon half the cornmeal mixture into the prepared dish. Spread out with the back of a wet spoon to cover the bottom and sides completely; set aside. Cover and keep remainder of cornmeal mixture warm and set aside.
Heat bacon drippings in a large skillet over medium heat. Add onions, peppers, and garlic and cook, stirring often, until softened, 7-8 minutes. Increase heat to medium-high; add beef, chili powder, and cumin; cook until meat is no longer pink, about 5 minutes. Add tomatoes and salt to taste and cook until most of the liquid has evaporated, about 8 minutes.
Spoon filling into casserole evenly, then top with remaining cornmeal mixture, spreading it out with the back of the wet spoon to cover filling. Bake until the top is crisp and sides are bubbling, 30-35 minutes.