Heat oven to 400 degrees.Grease pie plate,10 x 1 1/2".Cook and stir beef and onion in 10" skillet until beef is brown;drain.Stir in salt and pepper;spread in plate.Beat baking mix,milk and eggs with wire whisk or hand beater until almost smooth,about 1 minute. Pour into plate. Bake 25 minutes.Top with tomatoes and cheese.Bake until knife inserted in center comes our clean,5 to 8 minutes.Cool 5 minutes. Top with lettuce and pickles.Makes 6 to 8 servings.