In a medium bowl, combine the cooked ground beef, diced onion, refried beans, and taco seasoning. Mix well until everything is thoroughly combined.
To a large, oven-safe skillet or baking dish, spread about one-third of the tortilla chips. Top with half of the beef-bean mixture, then sprinkle with one-third of the shredded cheeses and one-third of the black beans. Repeat the layers one more time.
Bake in the preheated oven for about 10 minutes, or until the cheese is melted and bubbly.
Once baked, carefully remove from the oven. Top the nachos with diced tomato, diced avocado, sliced scallions, chopped cilantro, and jalapeños. Drizzle with sour cream.
Notes
Serve immediately and enjoy your delicious homemade nachos!