In a small bowl, combine salsa and beans. Arrange a third of the tortilla strips in a greased 11x7-in. baking dish. Layer with a third of the cheese and half of the salsa mixture. Repeat layers. Top with remaining tortilla strips., In a large bowl, whisk eggs, egg whites, milk, sour cream, onions and salt; pour over top. Sprinkle with remaining cheese. Refrigerate, covered, at least 8 hours or overnight., Remove from refrigerator 30 minutes before baking. Preheat oven to 350°. Bake, covered, 30 minutes. Uncover; bake 10-15 minutes longer or until a knife inserted in the center comes out clean. Let stand 5 minutes before serving.