Preheat oven to 375. Spray a 9x9 inch baking pan with nonstick spray
In a large skillet, brown ground beef. Drain.
Add taco seasoning and water and simmer until thick and flavors blend. about 5 minutes. Add in refried beans if you are using them. Mix until well combined
Place 2 whole tortillas in bottom on baking pan, then cut one in half and fit it in to cover bottom
Layer 1/2 of the meat mixture over the tortillas, then 1 cup of salsa over the meat, then 1/2 of the cheese. At this point, if you would like to add in black beans, corn, etc, you can. Repeat layers, tortillas again, the rest of the meat, 1 cup salsa, 1/2 the cheese, any "add ins" and end with tortillas. Top with remaining 1/2 cup salsa. Cover and bake for 25-30 minutes, uncovering the last 5 minutes.
Cut into 4 servings, garnish each with 2 Tbsp sour cream.