Preheat the oven to 350 degrees F (175 degrees C). Lightly grease a 9x13 inch pan; set aside.
Heat a large skillet over medium-high heat and stir in the ground beef and onions. Cook and stir until the beef is crumbly and evenly browned. Drain fat. Mix in the taco seasoning, and set aside.
Spread the refried beans to cover the bottom of the prepared 9x13 inch pan. Layer the cooked ground beef and onions evenly over the refried beans. Pour the jar of salsa over the ground beef and spread 2 cups shredded Cheddar cheese over the salsa layer.
Bake in the preheated oven until the cheese is bubbly and the layers are heated through. Serve with tortilla chips and your choice of fresh toppings.