1Preheat oven to 400 degrees F (200 degrees C). Grease a deep-dish 9-inch pie dish.
2Heat a large skillet over medium-high heat. Cook and stir beef and onion in hot skillet until browned and crumbly, 5 to 7 minutes; drain and discard grease. Spread ground beef mixture into the prepared pie dish.
3Blend milk, baking mix, eggs, Italian seasoning, salt, and pepper together in a blender until smooth, about 15 seconds; pour over beef mixture.
4Bake in the preheated oven until biscuit topping is lightly browned, about 25 minutes. Arrange tomato slices on biscuit topping; sprinkle with Cheddar cheese. Continue baking until cheese is melted, 5 to 8 more minutes. Cool 5 minutes before slicing.
Footnotes
Tip
Aluminum foil helps keep food moist, ensures it cooks evenly, keeps leftovers fresh, and makes clean-up easy.