PREHEAT oven to 350°F. Line an 8- or 9-inch loaf pan with Reynolds Parchment Paper; set aside.
COMBINE ground turkey, 1/4 cup spaghetti sauce, bread crumbs, onion, eggs, Parmesan cheese and fennel in a bowl.
PRESS half of turkey mixture into parchment-lined pan. Press a 1 inch indentation down center of mixture, leaving 1-inch thickness on all sides.
TOSS spinach and Mozzarella cheese together in a bowl; spoon into indentation, mounding in center. Press remaining turkey mixture evenly over top, sealing edges.
BAKE 45 to 50 minutes. Spoon remaining spaghetti sauce over meat loaf. Bake 15 minutes more. Let stand 10 minutes.
Reynolds Kitchens Tip: The quickest way to line an 8 or 9-inch loaf pan is to cut one 5 inch sheet of parchment and one 8 or 9 inch sheet of parchment. Place these sheets in pan, criss crossing at the center. Trim any excess parchment that extends above edge of pan.