A cup of low-fat Greek yogurt whisks with snipped fresh chives, Dijon mustard, salt, and pepper into a dressing that coats torn romaine without making it heavy. Eight ounces of lump crabmeat, two seeded tomatoes, and a chopped avocado arrange over the lettuce before the dressing spoons on top. Four servings in 15 minutes. The Greek yogurt base keeps the salad from feeling dense, letting the crab stay the dominant flavor rather than getting buried under richness.