Sauté the sliced onion and garlic in a frying pan over medium heat. Add the minced beef and chili powder and brown and break it up with a fork or spatula. Season with salt and pepper.
Preheat oven at 200˚C (400˚F) and meanwhile make the guacamole
Take an ove dish and make a big layer of the nachos. Add half of the ground beef on top and some cheese. Add another layer of the nachos and add the second half of the beef and more cheese. If you're using the beans you want to add them to the beef layer so they warm through in the oven.
Place the oven dish in the oven until the cheese has melted. Roughly 10 minutes. Sprinkle over the spring onion, the tomatoes and chili peppers. Serve with the guacamole and sour cream.