Place ground beef in a large, deep skillet. Cook over medium high heat until evenly brown. Drain, then season with taco seasoning, garlic, cayenne pepper, chili powder and water. Simmer for 10 minutes.
Preheat oven to 375 degrees F (190 degrees C). Grease the bottom of a 9×13 inch baking dish.
Place 6 tortillas into the prepared baking dish. Spread 1/3 of the salsa on top of the tortillas. Spread 1/2 of the meat mixture evenly over the salsa. Sprinkle with 1/2 of the green onions. Drop 1/2 of the sour cream randomly over the green onions. Top with 1/2 cup Cheddar and 1/2 cup Monterey Jack cheese. Repeat layers. Top with 6 tortillas, spread with remaining salsa, and sprinkle with remaining cheese.
Bake in a preheated oven for 30 to 45 minutes or until cheeses are melted.