In a large skillet over medium-high heat, cook onion in butter until softened and starting to brown a bit. Add in beef, green chiles, chili powder, cuin, salt, and garlic powder. Cook beef until browned.
Reduce heat to low and add pinto beans, black beans, and salsa into the beef mixture. Stir until combined and let cook for just a few minutes.
Line the bottom of a 9x13 dish with 4 cups of corn chips. Sprinkle with 2 cups of cheese. Spoon ground beef and bean mixture on top of the cheese layer. Sprinkle with 2 extra cups of cheese.
Bake at 350, uncovered, until bubbly and cheese is browning, about 25-30 minutes. Garnish with additional toppings as desired.