Pat the duck dry using paper towels. Trim off any excess fat opposite the cavity. Score the breast skin in a criss-cross pattern carefully without piercing the meat.
Stuff the cavity with quartered onion, lemon, and herb sprigs, then tie the legs together. Pat dry again and generously sprinkle salt all over.
Place the duck uncovered in the refrigerator for at least 8 hours or up to a day for extra crispy skin.
Remove duck 30 minutes before roasting to bring to room temperature. Preheat oven to 425°F.
Mix paprika, pepper, and garlic powder and rub evenly over the duck.
Line roasting pan with foil and place a rack inside. Set duck on rack and insert leave-in meat thermometer into thigh.
Roast at 425°F for 15 minutes, then reduce temperature to 350°F and continue roasting until internal temperature reaches 165°F (about 1 hour 15 minutes).
Remove duck from oven, tent loosely with foil, and rest for 10 to 15 minutes before carving.

Cranberry-Orange Glaze:
Combine cranberry juice, orange juice, molasses, cinnamon sticks, grated garlic, grated ginger, balsamic vinegar, salt, and cayenne in saucepan.
Bring to boil over medium-high heat, then simmer until slightly reduced.
Whisk cornstarch with cold water until smooth and gradually add into sauce to prevent lumps.
Bring back to boil and whisk until thickened, about 1 minute.
Remove from heat and stir in fresh orange zest.
Brush some glaze on duck during last 15 minutes of roasting and serve remaining glaze alongside.