Brown the beef and onions together. Place can of beans in casserole first ( I use a glass baking dish). Put 1/2 Doritos on top of beans. Next layer the meat and onions. Cut up the Velvetta on top of the meat and onions. Add the rest of the Doritos.
Mix the rotel and chicken soup and put on top- season with the salt and pepper. Cover with foil (tent-like). Bake at 400 degrees for 30-40 minutes until the cheese is melted.