In large non-stick skillet, heat oil over medium heat. Add onions;cook until tender but not browned, about five minutes. Stir in garlic,spinach, salt and pepper and cook just until spinach starts to wilt,about three minutes. Remove from heat.
Add cooked rice to spinach and stir in lemon zest until well combined.
Spread spinach mixture evenly over salmon and sprinkle with cheese and walnuts. Roll up gently using toothpicks or butcher’s twine to secure.
Place walnut stuffed salmon on a parchment-lined rimmed baking sheet and bake in a 375ºF(190ºC) oven until fish is cooked through, about 15-20 minutes.
Transfer to cutting board and let rest 10 minutes before slicing. Serve with steamed seasonal vegetables or a green salad.
Per serving: 378 calories, 24 g protein, 24 g total fat, 5 g saturated fat, 11 g polyunsaturated fat, 7 g monounsaturated fat, 57 mg cholesterol, 17 g carbohydrate, 4 g fibre, 419 mg sodium