Line slow cooker with foil, leaving 6-inch overhang "handles" to easily lift out the cooked taco stack.

In a large skillet over medium-high heat, brown the ground beef until no pick remains. Drain if needed.

Stir in taco seasoning and cook for 1 minute.  Add tomato sauce and cook for another 2 - 3 minutes until hot.

Spread one side of six tortillas with a thin layer of butter. Lay one tortilla, butter side up, in the slow cooker on top of the foil.

Spread about 1/2 cup of the taco meat mixture over the tortilla. Use a spoon to spread it out to the edges. It doesn't have to be perfect- you'll just want to have enough meat to make six layers. Sprinkle 1/2 cup of the cheese over the meat. Then lay another buttered tortilla over the cheese. Repeat the steps until all of the tortillas are stacked with meat and cheese. Sprinkle remaining cheese over the top tortilla.

Loosely fold the foil inward to cover taco stack. Cover with lid.  Cook on High for 1 hour. Dinner is ready to eat when all of the cheese has melted.

Garnish with Pico De Gallo, Sour Cream and Cilantro (optional)