If you need to make a quick dinner, this is sure to be a great pleasure. However, this is only a template. You could make a dish that is even more memorable by making some of these ingredients yourself. Homemade corn tortillas? Yes. Heirloom beans from Rancho Gordo, braised with leaf lard, then refried yourself? That would be tremendous. Adding roasted poblanos or Spanish chorizo to the mix? You can’t go wrong. Think of this as the first step. Make it again your own way next time.
Prepare to bake. Heat the oven to 450°.
Brown the beef. Set a large skillet over medium-high heat. Pour in the oil. When the oil is hot, add the ground beef. Cook, stirring occasionally, until the beef is entirely browned, about 10 minutes.
Take the beef out of the pan, leaving oil and fats behind. Add the chopped onion and garlic. Cook, stirring occasionally, until the onion and garlic are soft and translucent, about 10 minutes. Add the cumin and chili powder and stir to coat the onions. Add the beef back to the pan and toss with the onion, garlic, and spices to coat. Move the beef to a large bowl.
Assemble the casserole. Line the bottom of a baking pan with some of the corn tortillas. Scoop in 1/3 of the ground beef, 1/3 of the refried beans, 1/3 cup of each of the cheeses, 1/3 of the olives, and 1/3 of the salsa. Top that with another layer of corn tortillas, and repeat. Finish with another layer of tortillas and filling. Top with the remaining cheeses.
Bake the casserole. Bake the casserole until the cheese on the top is golden and bubbly and everything is heated through, about 40 minutes. Take the casserole out of the oven and slather the top with the sour cream, then the avocado.