Preheat oven to 400°F. Stir together harissa, 1 tbsp. olive oil, lemon juice and half of the salt; rub all over pork tenderloin.
Transfer to foil-lined baking sheet and let stand for 15 minutes.
Roast for 15 to 20 minutes or until internal temperature reaches 160°F. Tent with foil and let stand for 10 minutes. Slice crosswise.
Meanwhile, cook pasta according to package directions; drain well.
Heat remaining oil in skillet set over medium-high heat; cook onion for 5 minutes. Add spinach, orange zest, remaining salt and chicken broth; cook for about 3 minutes until spinach wilts. Add tagliatelli and toss to coat. Serve with pork tenderloin slices.
Recipe Notes
Tip:
Look for harissa paste in the condiment aisle, where specialty Middle Eastern foods are sold or online.