How to Make It
Light a grill. In a small bowl, pour the lemon juice over the minced shallot and let stand for 5 minutes. Whisk in 2 tablespoons of the olive oil and season the dressing with salt and pepper.
Using a sharp knife, peel the grapefruit, making sure to remove all of the bitter white pith. Working over a medium bowl, cut in between the membranes to release the sections into the bowl. Toss the fennel and parsley with the grapefruit.
Brush the scallops with the remaining 1/2 tablespoon of olive oil and season with salt and pepper. Grill over moderately high heat, turning once, until just cooked through, about 5 minutes.
Toss the dressing with the salad and season with salt and pepper; transfer to plates. Set the scallops on the salads and serve.