This refreshing salad really perks up winter lunches and dinners.
Use a sharp knife to cut skin (and white pith) from grapefruits; cut into segments, reserving juice.
Place lettuce in a large bowl with avocado. Drizzle with 1 to 2 tablespoons reserved grapefruit juice, olive oil, and vinegar. Season with salt and pepper; toss gently. Top with grapefruit segments.
Choose heavy, undamaged avocados. One that yields slightly to pressure is best for slicing and dicing; if pressure leaves a small indentation, the avocado is best mashed.