Combine first 4 ingredients in a spice grinder; process until powdered. Place in a small bowl; stir in ginger, garlic, red pepper, and cinnamon. Add the vinegar, stirring until combined. Place vinegar mixture and duck in a large zip-top plastic bag; seal. Marinate in refrigerator 4 hours or overnight.
Heat vegetable oil in a large nonstick skillet over medium-high heat. Add onion, and sauté 6 minutes or until browned. Add coriander and turmeric; sauté 1 minute.
Add duck to pan; cook 3 minutes on each side. Stir in water, tomato paste, salt, and potatoes, and bring to a boil. Cover, reduce heat, and simmer 20 minutes or until duck is done and potatoes are tender. Remove from heat. Remove duck from pan; cut duck diagonally into 1/2-inch-wide slices. Add sugar to pan; stir to combine. Return duck to pan; stir to combine.