Heat oven to 400°F. Melt butter in large skillet over medium heat. Stir in taco seasoning mix. Add beef strips; cook and stir 5 to 6 minutes or until of desired doneness. Drain.
Meanwhile, place refried beans in microwave-safe dish. Microwave on HIGH for 2 minutes, stirring once or twice.
Spread each tortilla with refried beans to within 1/4 inch of edge. Top each with beef, Cheddar cheese and onions. Roll up, folding in sides. Place, seam side down, in ungreased 13x9-inch (3-quart) glass baking dish. Pour enchilada sauce over burritos. Sprinkle with Mexican cheese blend.
Bake at 400°F. for 7 to 12 minutes or until burritos are thoroughly heated and cheese is melted.