Preheat the oven to 400°F. Brush the peppers (inside and outside) with the olive oil and sprinkle with the salt, pepper and garlic powder. Place the peppers on a baking sheet and roast for 15 to 20 minutes.
While the peppers are roasting, make the turkey taco meat. Heat a large skillet over medium heat and add the olive oil. Add the diced peppers, shallot and garlic with a pinch of salt. Cook, stirring often, until softened, about 5 minutes.
Add in the ground turkey, breaking it apart with a wooden spoon. Season it with the cumin, paprika, chili powder, garlic powder, salt and pepper. Stir well, continuing to break apart the meat into small crumbles. Cook until the turkey has browned.
Add the water and flour to a shaker bottle and shake for 30 seconds. Pour the mixture into the tacos, stirring well and cooking for another 5 to 6 minutes, until saucy.
Remove the peppers from the oven. Fill the peppers with the turkey taco mixture.