Seared Scallops and Butter Lettuce Salad with Grapefruit Vinaigrette

3/4 pound medium sea scallopsKosher salt and ground black pepper1 cup Wondra or all-purpose flour, for dredging#189; cup vegetable oil, divided#8531; cup grapefruit juice1 small shallot, finely chopped1 tablespoon unseasoned rice vinegar#8539; teaspoon sugar2 small heads butter lettuce, torn into bite size pieces1 ripe avocado, pitted and sliced1 small pink grapefruit, peeled and sectioned, with each section halved.1 medium scallion, green part only, thinly sliced crosswise#188; cup sunflower seedsSeason the scallops with salt and pepper. Spread the Wondra or flour on a plate, then dredge the scallops through it, shaking off any excess.In a large skillet over medium, heat 2 tablespoons of the oil. Add the scallops to the skillet and saute for 2 to 3 minutes per side, or until cooked through. Transfer the scallops to a plate and let stand until they are at room temperature.In a small saucepan, simmer the grapefruit juice until it reduces to 2 tablespoons. Transfer to a small bowl. Add the shallot, rice vinegar, sugar and 1/4 teaspoon of salt. Whisk until the sugar and salt have dissolved. Slowly whisk in the remaining vegetable oil, then whisk in the juices that have accumulated on the scallop plate until the dressing reaches the desired consistency.Toss the lettuce with 1/3 cup of the dressing. Mound the lettuce over 4 plates and top with the scallops, avocado and grapefruit. Sprinkle with the scallions and sunflower seeds, and drizzle with the remaining dressing.Serves four.@Recipe nutrition:Nutrition values per serving: 604 calories, 41 g fat (6 g saturated), 41 g carbohydrates, 6 g fiber, 22 g protein, 28 mg cholesterol, 275 mg sodium."Sara Moulton's Everyday Family Dinners" (2010 Simon Schuster)