Impossible Cheeseburger Pie

1 lb. ground beef
1 1/2 c. chopped onion
1 1/2 c. milk
3 eggs
3/4 c. Bisquick baking mix
1/2 tsp. salt
1/4 tsp. pepper
2 tomatoes, sliced
1 c. shredded cheddar cheese

Heat oven to 400 degrees. Grease pie plate, 10 x 1 1/2 inches. Brown beef and onion; drain. Spread in plate. Beat milk, eggs, baking mix, salt and pepper 15 seconds in blender on high or 1 minute with hand beater. Pour into plate. Bake 25 minutes. Top with tomatoes and cheese. Bake until knife inserted in center comes out clean, 5 to 8 minutes. 6 to 8 servings. High Altitude: Increase first bake time to 30 minutes.

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