Heat diced onions and ground meat in a large skillet over medium-high heat. Cook until meat is browned and onions are soft. Drain any excess liquid.
Lower the heat and stir in the taco sauce. Use a potato masher to break the meat into smaller pieces. Remove from heat.
In a medium sized bowl, combine the refried beans and salsa. Spread the bean mixture onto the bottom of a 9x9 inch baking dish or 9" cast iron skillet.
Place 1/2 of the bag of Fritos into a plastic bag and crush them with your hands. Sprinkle crushed Fritos evenly over the bean mixture.
Layer the meat over the crushed Fritos, followed by the shredded cheese. Bake 15 minutes until cheese is melted.
Remove from oven. Top with remaining Fritos and your toppings of choice (shredded lettuce, diced tomatoes, chopped scallions, etc.)