Preheat the oven and dice the onion - Preheat the oven to 400℉, convection bake setting. Finely dice the onion.
Sauté the onion and beef - Heat the olive oil then add the onion. Sauté until soft, then add the beef and continue cooking until the beef is thoroughly browned.
Finish the filling - Once the ground beef is cooked, add the spices, cornstarch and tomato paste to the pan. Stir to combine, and then add the water. Cook for a few minutes until the mixture is slightly thickened.
Assemble and bake - Spread the refried beans evenly across the bottom of the pie crust, then top with the beef mixture. Top that with salsa, and then cheese. Bake for approximately 20 minutes or until the cheese is melted.
Prepare the taco toppings - While the Taco Pie is baking, chop the scallions, slice the olives, chop the lettuce, prep the avocado, and slice the radishes.
Garnish and serve - If you're feeding a group, it would be nice to add the toppings to the pie, then cut and serve at the table. Or you could serve slices and pass the taco topping platter around so that your friends can customize their own.
Notes
My gluten-free recipe for Masa Harina Pie Crust is found on my Crust and Pastry Variations Page. I recommend that you try my Tomatillo Salsa recipe as well!