Heat oven to 400°. Grease pie plate, 10”x 1 ½ “.
Cook and stir beef and onion over medium heat until beef is brown; drain, spread in plate.
Beat milk, baking mix, eggs, salt and pepper until smooth, 15 seconds in blender on high. Pour into plate.
Bake 25 minutes.
Top with tomatoes; sprinkle with cheese. Continue baking until knife inserted in center comes out clean, 5 – 8 minutes.
Cool 4 minutes.