Place beef mince in a large, deep frypan. Cook over medium high heat until evenly brown. Drain then season with taco seasoning, garlic, cayenne pepper, chilli powder and water. Simmer for 10 minutes.
Preheat oven to 190 degrees C. Grease the bottom of a 20x30cm 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 spring onions. Drop 1/2 of the sour cream randomly over the spring onions. Top with 1 cup 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.