In a large skillet, heat olive oil over medium-high heat. Add ground beef and chopped onion, cooking until meat is browned and onion is softened, then drain excess grease.

Stir in minced garlic and cook for one minute until fragrant.

Add taco seasoning, tomato sauce, and diced tomatoes with green chilies to the skillet, stirring well to combine.

Bring to a simmer; reduce heat to low and cook for 5-7 minutes to meld flavors and thicken the sauce.

Preheat oven to 375°F (190°C) and lightly grease a 9x13 inch baking dish.

Pour half of the red enchilada sauce into a shallow bowl for dipping.

Dip each corn tortilla briefly into the enchilada sauce to make it pliable and flavorful.

Lay two dipped tortillas side-by-side in the prepared baking dish, overlapping slightly.

Spread approximately one-third of the meat mixture over the tortillas.

Sprinkle generously with about half a cup of shredded cheese.

Repeat the layering process with dipped tortillas, meat mixture, and cheese until all meat filling is used.

For the top layer, place the remaining dipped tortillas, pour over any remaining enchilada sauce, and sprinkle with the rest of the shredded cheese.

Cover the baking dish loosely with aluminum foil and bake for 20 minutes.

Remove the foil and bake for an additional 10-15 minutes until the cheese is melted and bubbly, and the edges are lightly browned.

Let the casserole rest for 5-10 minutes before serving to help it set for cleaner slices.