In a large skillet, brown the ground beef over medium-high heat, then drain any excess fat. Mix in taco seasoning, minced garlic, chili powder, and cayenne pepper, adding water and letting it simmer on low for about 10 minutes.
Preheat your oven to 375°F (190°C) and lightly grease a 9x13-inch baking dish.
Begin layering by placing 6 tortillas in the bottom of the dish. Spread a third of the salsa over the tortillas, followed by half of the beef mixture, a portion of the chopped green onions, dollops of sour cream, and a mix of Cheddar and Monterey Jack cheeses.
Repeat the layering process, then finish with another set of 6 tortillas, the remaining salsa, and top with any leftover cheese.
Bake in the oven until the top is golden and bubbly, approximately 30 to 45 minutes.