In a large skillet over medium heat, brown ground beef. Drain grease. Add water and taco seasoning to the ground beef. Mix and simmer for a 2-3 minutes.
Add refried beans and ½ cup of salsa to the taco beef mixture. Stir to combine. Remove from heat.
In a separate medium bowl, combine 1 cup salsa with 1 cup sour cream. Stir and mix well.
Preheat the oven to 350°F. Then spray a 9x13-inch casserole dish with cooking spray. Lay 2 tortillas in the bottom of the baking dish.
Spread ⅔ cup sour cream mixture over tortillas.
Spread ⅓ of taco beef mixture over sour cream layer.
Sprinkle 1 cup shredded cheddar cheese over top of beef mixture.
Layer with 2 more large tortillas. We tear the tortillas to make sure all parts of the cheese layer are covered without the tortilla going up the side of the dish.
Repeat sour cream, taco beef mixture and shredded cheese layers. Layer with 2 more tortillas. Then again, repeat the sour cream, taco beef mixture layer. And finally, top with 2 cups shredded cheddar cheese.
Bake uncovered for 15-20 minutes or until the cheese is melted in all the layers. Remove from oven.
Optional: sprinkle with cilantro and fresh diced tomatoes.