Place the tortilla halves in the muffin tin cavities, creating small baskets. (You are basically just pushing them in and maneuvering them to fit. If you see them tearing in a couple places, that is normal. It might help to microwave the tortillas for 15 seconds or so to make them more flexible.)
Bake them in the preheated oven until crispy, about 20 minutes. Keep an eye on them! Let cool.
Heat the olive oil in a skillet over medium heat. Add the chopped onion and green onion, and cook for 5 minutes.
Add the ground meat and cook until fully cooked. Mix in the cumin powder and Mexican spice blend. Season with salt and pepper, to taste.
In a bowl, mash the avocado and mix it with the lemon juice. Add salt and pepper, to taste.
Fill the tortilla baskets with the ground meat, tomatoes, mashed avocado and fresh cilantro. Serve!