Preheat the oven to 350°F.
In a large skillet, brown the beef with onions over medium-high heat. Transfer the browned beef to a colander and drain the fat.
Add the browned beef back into the skillet. Season with garlic, cumin, salt, and black pepper. Add chopped green chilies, stir for 2 minutes or until the liquid is absorbed. Add diced black olives, stir to combine then turn off the heat.
In a skillet, heat ½ cup of oil over medium heat. Fry the corn tortillas until soft (about 5-7 seconds on each side). Drain on a paper towel-lined plate.
Spread about ½ cup of red enchilada sauce over the bottom of a 9x13-inch casserole dish. Working one at a time, spread a small amount of sauce on top of the tortilla. Add some of the meat mixture, green onions, and cheese then roll up the tortilla.
Place the rolled tortilla in the baking dish, repeat with the rest of the tortillas then pour the remaining sauce on top. Sprinkle with the remaining shredded cheese, chopped green onions, and 1 tbsp of diced black olives. Bake for 15-20 minutes or until bubbly. Serve with toppings of your choice.