Preheat oven to 400 F.
Cut the tops off the bell peppers, scoop out the seeds, and stand them up in a baking dish.
Place the peppers in the oven (empty) for twenty minutes while you prepare the filling.
While the peppers are softening in the oven, heat the oil in a large pan over medium-high heat, then saute the red onion for a few minutes until translucent.
Add the ground turkey, garlic, spices, and salt, and saute, stirring frequently, until the turkey is no longer pink, about ten minutes.
Add the tomatoes, and cook a few more minutes to blend flavors.
Stir in the rice.
Remove the peppers from the oven, and spoon the turkey and rice mixture inside until they're filled to the top.
Return the peppers to the oven, and cook for 20 minutes.
Remove the peppers again, sprinkle cheddar evenly on top of the peppers, then return to the oven once more, for 10 minutes.
Tuck the scallions into the peppers (if using) to look like handles on your Pot O' Gold. Serve and enjoy!