Mix orange zest, nutmeg, salt and pepper and rub all over roast. Refrigerate roast uncovered overnight. Remove from fridge 1 hour before cooking.
Preheat oven to 425°F. Preheat cast iron pan on high heat and add oil.
When oil begins to smoke, sear coullote on all 6 sides about 2-3 minutes per side. Remove from pan and set aside. Lower heat to medium.
Toss parsnips with honey, olive oil, rosemary, salt and pepper and place in cast iron pan. Sear for 1 minute without moving.
Stir parsnips once, place coulotte on top and put in oven.
Roast for 10-15 minutes or until internal temperature of the coulotte is 125°F. Then remove from pan and set on wire rack to rest for at least 10 minutes.
While the coulotte rests, stir parsnips again and continue to roast until tender, about 10 more minutes.
Slice top sirloin cap thin and against the grain. Drizzle with olive oil and a sprinkle of salt. Serve over roasted parsnip. Happy eating!