Preheat the oven to 350°F (175°C).
Grease a 9-inch pie dish or a similar baking dish with oil or butter.
Sauté the aromatics. Heat the avocado oil in a large skillet over medium heat. Add the onion and bell pepper. Cook 4–5 minutes, until softened.
Stir in the garlic and cook 30 seconds, until fragrant.
Brown the beef. Add the ground beef to the skillet. Break it up with a spoon and cook until no longer pink, about 5–7 minutes. Drain excess fat if needed.
Season the meat. Stir in chili powder, cumin, paprika, oregano, salt, pepper, and cayenne (if using).
Add tomato paste and 2–3 tablespoons water. Simmer 2 minutes to coat the meat and develop flavor. Taste and adjust salt.
Whisk the custard. In a bowl, whisk eggs and heavy cream until smooth.
Season with a pinch of salt and pepper.
Assemble the pie. Spread the beef mixture evenly in the pie dish. Sprinkle 1 cup of the cheese over the meat. Pour the egg mixture on top, tilting the dish so it settles in.
Top with remaining 1/2 cup cheese and the olives.
Bake. Place the dish on the center rack and bake 25–30 minutes, until the center is set and the top is golden. A knife inserted near the center should come out mostly clean.
Rest and garnish. Let the pie rest 10 minutes to firm up. Sprinkle with fresh cilantro.
Slice and serve with lettuce, tomatoes, avocado, sour cream, and a squeeze of lime.