Start by gathering all your ingredients. Chop the onion, mince the garlic, and have your ground beef ready. Preheat your oven to 350°F (175°C) while you prepare the filling.
In a large skillet, heat the avocado oil over medium heat. Add the finely chopped onion and sauté for about 3 minutes until it becomes translucent. Add the minced garlic and cook for an additional minute until fragrant.
Add the ground beef to the skillet, breaking it up with your spatula. Cook until browned, approximately 5-7 minutes. Stir in the chili powder, broth or water, and sea salt. Allow the mixture to simmer for about 5 minutes until slightly thickened.
In a 9x13-inch baking dish, spread a thin layer of red enchilada sauce on the bottom. Place 4 corn tortillas on top, overlapping them as necessary. Spoon half of the beef mixture over the tortillas, sprinkle with half of the grated colby jack cheese, and drizzle with more enchilada sauce. Repeat the layering process with the remaining tortillas, beef mixture, cheese, and sauce.
Cover the baking dish with aluminum foil and bake in the preheated oven for 20 minutes. After 20 minutes, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden brown.
Once baked, remove the casserole from the oven and let it cool for a few minutes. Top with chopped fresh tomatoes, diced avocado, a dollop of sour cream or plain Greek yogurt, and fresh cilantro before serving.
