Yield: 4 servings.

1 medium-sized red onion, thinly sliced in half rings
¼ cup red wine vinegar
1 tsp. sugar
1 tsp. salt, divided
¼ tsp. ground black pepper, divided
3 Tbsp. olive oil, divided
1½ lb. salmon fillet, cut crosswise in 4 portions
6 cups lettuce leaves in bite-sized pieces
1 cup fresh blueberries

In microwaveable cup, combine onion, red wine vinegar, sugar, ½ tsp. salt and 1/8 tsp. pepper. Cover loosely with plastic wrap and microwave on high power for 1 minute. Let stand, stirring occasionally, until onions turn pink, about 15 minutes. Meanwhile, preheat grill or broiler. Brush 1 Tbsp. olive oil on both sides of salmon fillets. Sprinkle with remaining ½ tsp. salt and 1/8 tsp. pepper. Grill or broil salmon, skin-side down, until just cooked through, about 6 minutes.