Heat oven to 400ºF. Spray bottom and sides of 13x9-inch pan with cooking spray or grease with shortening. In medium bowl, mix flour, cornmeal, sugar, baking powder and 1/4 teaspoon salt. In small bowl, stir together milk, oil and egg. Add egg mixture all at once to flour mixture; stir just until moistened. Spread batter in pan. Bake 10 to 13 minutes or until light golden brown.
Meanwhile, in 10-inch nonstick skillet, cook sausage, bell pepper and onion over medium-high heat 5 to 7 minutes, stirring occasionally, until sausage is no longer pink; drain. Remove sausage from skillet; keep warm.
In medium bowl, beat eggs, milk, salt and pepper with fork or wire whisk until well mixed.
In same skillet, heat butter over medium heat just until butter begins to sizzle. Pour egg mixture into skillet. As mixture begins to set at bottom and side, gently lift cooked portions with spatula so that thin, uncooked portion can flow to bottom. Avoid constant stirring. Cook 3 to 4 minutes or until eggs are thickened throughout but still moist.
Arrange eggs over hot crust; top with sausage mixture. Sprinkle with cheese. Bake 5 to 7 minutes or until cheese is melted. Serve with salsa.