Heat a large skillet over medium high heat. Add 1 1/2 teaspoons of oil to the pan; swirl to coat. Sprinkle the shrimp with 1/4 teaspoon salt and 1/8 teaspoon pepper. Add the shrimp to the pan. Cook for 3 minutes or until the shrimp are done, stirring frequently. Keep warm.

Step 2

Peel and section the grapefruit over a bowl, reserving 3 tablespoons of the juice.

Step 3

Combine the grapefruit juice, remaining 2 tablespoons oil, remaining 1/4 teaspoon salt, remaining 1/8 teaspoon black pepper, tarragon, brown sugar, and shallots in a large bowl, stirring well with a whisk. Add the lettuce and toss.

Step 4

Arrange 2 cups of the lettuce mixture on each of 4 plates. Top each serving with 3 avocado wedges; divide the shrimp and grapefruit sections evenly among the servings.