Preheat oven to 350 degrees. Place oven rack in the middle position and line a large baking sheet with parchment paper. Place the bell pepper slices onto the pan.
In a pan over medium heat, heat 1 tablespoon oil. Add in ground beef and taco seasoning, and using a spatula, break up the ground beef as it cooks, until no longer pink, about 8 to 10 minutes.
Place the bell pepper slices in the oven for about 5 minutes. Remove from the oven onto the counter and top with meat mixture and salsa. Add the cheese on top, if using, black olives, and any other toppings you want to be heated.
Place back into the oven and bake until the cheese is melted about 5 minutes.
Remove from the oven and allow to cool before serving.