Trim away the fat cap from the pork. In a small bowl combine the rosemary, salt, cumin, pepper, and cinnamon, then rub all over the pork. Let stand at room temperature for 1 hour, or wrap in plastic and refrigerate for up to 1 day; bring to room temperature for at least 30 minutes prior to cooking.
When ready to cook, place a rack in the center of your oven and preheat to 450°F.
In the bottom of a large roasting pan with a rack, scatter the apples, onions, garlic, and rosemary sprigs (if you don't have a rack, you can form a few rings out of aluminum foil, then set the pork on that). Place the pork loin on top. Pour 1/2 cup of the broth around the pork.
Bake the pork for 15 minutes, then reduce the oven temperature to 300°F. Continue baking until the pork reaches 135°F on an instant read thermometer inserted at the thickest part, about 30 to 50 minutes more depending upon the weight of your pork (my 4 1/4-pound loin needed 43 additional minutes). Cover and let rest for at least 15 minutes (the pork’s temperature will rise as it rests).
While the pork rests, turn your oven to 350℉. Pour the remaining 1/2 cup broth into the hot pan and use a wooden spoon to stir the onions and apples. Return the pan to the oven and continue baking for 15 minutes while the pork rests to further soften the onions.
Thinly slice the pork. Serve with the apples and onions spooned over the top.
Notes
TO STORE: Refrigerate leftover pork roast, apples, and onions in an airtight storage container for up to 3 days.
TO REHEAT: Reheat leftovers in a covered baking dish in the oven at 350°F or in the microwave.
TO FREEZE: Freeze pork leftovers in an airtight freezer-safe storage container for up to 3 months. Thaw overnight in the refrigerator before reheating.
Nutritional information calculated based on a 3-pound roast.