Gently poach a large salmon fillet in water, wine, and aromatics then chill it and serve it with a creamy, flavor-packed yogurt sauce for an elegant dinner.
In a fish poacher or a pot large enough to hold the salmon, combine the wine, onion, celery, peppercorns, salt, and parsley.
Add 3 inches of water and bring to a boil. Add the salmon fillet (it should be fully submerged) and bring the water to a simmer. Cover and simmer gently over low heat until the salmon is just cooked through, about 8 to 9 minutes.
In a medium bowl, combine all of the cumin yogurt sauce ingredients and mix well.
Using two spatulas, carefully transfer the salmon fillet to a large platter. Dab off any white bits and let stand at room temperature for 15 minutes. Cover loosely with plastic wrap and refrigerate until cool.
Season salmon with salt and garnish with the lemon and cucumber slices. Serve it with the cumin yogurt sauce.