Grapefruit, Salmon, and Avocado Salad

skinless wild-salmon fillets (each about 8 ounces, 1 inch thick)

Coarse salt and freshly ground black pepper

extra-virgin olive oil

scallions, trimmed and thinly sliced

Ruby Red grapefruit, peel and pith removed, segmented

ripe avocado, pitted, peeled, and sliced

sunflower shoots, watercress leaves, or a combination of both

fresh lime juice