In a large skillet, heat the olive oil over medium heat. Add the diced onion and cook until softened, about 3-4 minutes.
Add the minced garlic and ground beef to the skillet. Cook until the beef is browned, breaking it apart with a spatula, about 5-7 minutes.
Drain excess fat from the skillet, then stir in the taco seasoning and water. Simmer for 5 minutes, allowing the flavors to meld.
Preheat your oven to 350°F (175°C). On a large baking sheet, spread out the tortilla chips in an even layer.
Evenly distribute the seasoned beef mixture over the chips. Sprinkle the black beans, diced tomatoes, and jalapeños on top.
Generously cover the nachos with shredded cheddar cheese.
Bake in the preheated oven for 10-15 minutes, or until the cheese is melted and bubbly.
Remove from the oven and top with dollops of sour cream, diced avocado, chopped cilantro, and sliced green onions.