3 salmon watercress yogurt dressing Recipes

celery stalk , cut into 2-inch pieces, scallions, greens sliced into 1/2-inch pieces, whites left whole, divided, lemon, halved: cut half into slices, zest and juice remaining half (1/2 tsp zest, 1 tbsp juice), divided, kosher salt, divided, freshly ground black pepper, divided, salmon fillets, skinned (about 2 inches thick ), plain low-fat yogurt, chopped fresh dill plus 1/2 cup fronds, divided, grated fresh horseradish, extra-virgin olive oil, watercress, thick stems removed (about 8 cups), sugar snap peas , thinly sliced crosswise (3 oz), radishes, sliced (1 1/2 cups)

fresh skinless salmon fillet or 1 1/4 lbs frozen skinless salmon fillet, mayonnaise or 1/2 cup salad dressing, plain yogurt, chopped red onion, capers, drained and chopped, shredded lemons , rind of, salt, very thinly sliced or thinly sliced firm-textured white bread, crust removed, loosely packed watercress, tops rinsed and dried (thick stems ), sliced pimento stuffed olive (optional)