Cook macaroni following package directions until al dente, firm but tender. Drain; rinse with cold water; drain again.
Preheat oven to 375 degrees F. Grease 13 x 9 x 2-inch baking dish.
Whisk together flour and 1/2 cup of the milk in medium-size saucepan until smooth. Add remaining milk, onion, garlic, mustard, salt and pepper. Cook over medium heat, stirring constantly, until mixture is thickened and bubbly. Boil 1 minute. Remove from heat.
Stir Cheddar and Parmesan cheeses, lemon juice and red-pepper seasoning into saucepan.
Combine macaroni and cheese sauce in large bowl. Pour into prepared baking dish.
Bake in preheated 375 degree F oven for 15 minutes. Combine bread crumbs, paprika and melted butter in small bowl. Sprinkle over top of macaroni. Bake 10 to 15 minutes longer or until bubbly and top is browned.