Start by heating the avocado oil in a large skillet over medium heat. Add the finely chopped onion and sauté until translucent, about 3-4 minutes. Stir in the minced garlic and cook for an additional minute until fragrant.
Add the ground beef to the skillet, breaking it apart with a spatula. Cook until browned and fully cooked through. Drain any excess fat if necessary.
Sprinkle in the chili powder, sea salt, and pour in the broth or water. Stir well to combine and let the mixture simmer for about 5 minutes until slightly thickened.
Preheat your oven to 350°F (175°C). In a 9x13-inch baking dish, spread a thin layer of the red enchilada sauce on the bottom. Layer 4 corn tortillas, followed by half of the beef mixture, a third of the grated cheese, and a third of the enchilada sauce. Repeat the layers, finishing with tortillas, the remaining enchilada sauce, and the last of the cheese on top.
Cover the baking dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbling and slightly golden.
Once out of the oven, let the casserole sit for about 5-10 minutes. Serve warm, garnished with fresh tomatoes, diced avocado, a dollop of sour cream or Greek yogurt, and a sprinkle of fresh cilantro.
