Fry ground beef with onions, pouring off excess fat. Stir in taco seasoning. Heat refried beans in a saucepan. Warm tortillas one at a time in a frying pan over medium heat, flipping them several times. Keep warm in a clean dish towel.
Fill tortillas with beef and/or beans, and let diners top the filling with lettuce, tomatoes, cheese, sour cream and salsa.