1. Place the seasoned bread crumbs on a shallow plate and set aside.
2. In a large bowl combine the tuna, half of the onions, onion powder, salt-free seasoning, parsley, whole-wheat bread crumbs, 2 tbsp sour cream, mustard, and egg whites. Mix well.
3. Form mixture into 4 patties with your hands. Press each into the seasoned bread crumbs, coating both sides. Set aside.
4. In a small saucepan, bring the water and remaining onions to a boil. Add couscous, cover, and remove from heat. Let sit for 5 minutes, then fluff with a fork.
5. Spray a large skillet with nonstick cooking spray. Place the skillet over medium-high heat and add the canola oil. When hot, add tuna patties and cook 3 to 4 minutes on each side until browned.
6. Mix the remaining 4 tbsp sour cream with the lemon juice, lemon zest, sugar, mayonnaise, and dill.
7. Top the tuna patties with lemon dill sauce and serve with hot couscous.
Makes 4 servings.