MIX egg product, milk and onion. Add to small nonstick skillet sprayed with cooking spray. Cook on medium heat 1 to 2 minutes or until set, stirring frequently.
SPOON egg product mixture evenly onto 2 of the muffin halves.
TOP each with 1-1/2 tsp. salsa and one 2% Milk Singles. Cover with remaining muffin halves.