For the spice rub:
3 tablespoons brown sugar
1 tablespoon sweet paprika
1 1/2 teaspoons salt
1 teaspoon ground black pepper
1 teaspoon onion powder
1 teaspoon garlic powder
Remaining ingredients:
2 pork tenderloins, approximately 1 pound each
3-4 red onions, peeled and halved, leaving stem ends intact
1-2 baking apples, cored and quartered (optional)
2-3 tablespoons olive oil, divided
Salt
Preheat your oven to 425 F and put your oven rack in the middle of the oven. Outfit your roasting pan with a rack and set aside. Mix all dry spice rub ingredients in a small bowl. Pat pork tenderloins dry and rub on all sides with olive oil. Rub spice rub on all sides of the tenderloins with your (clean) hands. Place tenderloins in the middle of your roasting pan/rack. Arrange onions and apples (if using), cut sides up around the tenderloins. Season onions and apples lightly with salt. Place roast in oven and cook for 25-30 minutes, or until the pork's juices run clear. Once cooked, remove roast from oven and let rest for 5 minutes.
To serve, slice tenderloins and add to a serving dish. Arrange onions/apples around the pork. Serve immediately.