Step 1

Heat the oven to 425°F and line a rimmed baking sheet. Arrange a rack in the middle of the oven and heat to 425°F. Line a rimmed baking sheet with aluminum foil.

Step 2

Brown the beef. Heat the oil in a large skillet over medium heat until shimmering. Add the beef, use a stiff spatula to break it up into large pieces, and season with the salt. Brown the meat undisturbed for 4 to 5 minutes. Break the meat up into smaller pieces with the spatula and and continue to cook until mostly cooked through, 2 to 3 minutes more.

Step 3

Cook the cheese sauce. Add the taco seasoning, garlic, and flour and stir to coat the beef. Add the milk and stir vigorously with the spatula, scraping the bottom of the pan as you stir -- the sauce should thicken right away. Cook until thickened, about 2 minutes. Remove from the heat. Add the cheese and stir until melted.

Step 4

Layer the nachos. Arrange about 1/2 of the chips on the baking sheet in an even layer. Evenly drizzle with 1/2 of the cheese sauce, then sprinkle with 1/2 of the shredded cheese. Top with the remaining chips, followed by the remaining cheese sauce and remaining shredded cheese. Sprinkle with the black beans and corn.

Step 5

Bake the nachos for 8 minutes. Bake the nachos until the cheese is melted and the chips around the edges are beginning to brown, about 8 minutes.

Step 6

Add the toppings. Just before serving, garnish the finished nachos with the red onion, jalapeño, Roma tomato, dollops of sour cream, and cilantro, if desired.