Preheat oven to 375 degrees. Coat inside of a 9 x 13 baking dish with 1 TBS melted butter.
In a large skillet over medium high heat crumble ground beef and add onion. Cook until beef is browned and onion is softened. Drain excess grease.
Stir in taco seasoning and water and allow to simmer for 2 minutes. Turn off heat.
Arrange 6 burrito size flour tortillas along the bottom and edges of prepared baking dish.NOTE: make sure bottom is totally covered with tortillas. Also allow excess tortillas to hang over the sides. Spread half of the nacho cheese sauce evenly onto the tortillas. Top with half of the meat mixture and spread evenly. Place 6 tostadas in a single layer on meat. They will overlap some.
Top evenly with tomatoes, cilantro and cheddar cheese. Top with remaining meat mixture evenly. Dollop sour cream & 1/2 of the remaining nacho cheese sauce all over the meat mixture.
Cover the top with the 2 remaining burrito size tortillas. Spread remaining nacho cheese on top. Wrap the edges of the tortillas that are overhanging from the sides of the dish to cover the top 2 tortillas.NOTE: use 1 regular size tortilla to cover any open space in the middle. Brush casserole with remaining melted butter and press down.
Bake in preheated oven for 30 minutes until golden brown and crispy. Let rest on stove top for 8 minutes. Invert & flip baking dish over onto a cutting board. Cut into squares using a serrated knife.
Top with tomatoes, sour cream, cilantro, cheese sauce, cheddar cheese, green onions, lettuce, olives, and/or taco sauce. Enjoy.
My mouth is watering