Crab, Grapefruit & Avocado Salad

Ingredients

• 1/2 cup plain non-fat yogurt
• 3 tbsp ketchup
• 1 tbsp light mayonnaise
• 1 tbsp fresh lemon juice
• 1/2 tsp tarragon
• 1/2 tsp salt
• 1/4 tsp cayenne pepper
• 6 cups bite-size pieces romaine lettuce
• 1 lb. lump crabmeat, picked over to remove any cartilage
• 2 cups cherry tomatoes, halved
• 2 pink grapefruits, peeled and sectioned
• 1/2 cup diced avocado