Preheat an indoor or outdoor grill to medium-high. Combine the first 5 ingredients in a small bowl. Whisk in the 4 1/2 Tbsp. olive oil and then set the dressing aside. Brush the salmon lightly with olive oil and season with salt and pepper. Lightly oil the bars of the grill. Grill the salmon 3 to 4 minutes on each side, or until just cooked through. Divide and arrange the spinach, tomatoes and bell pepper on 4 dinner plates. Set a piece of salmon in the centre of each plate, drizzle with dressing, and serve.