Place the salmon in a fish poacher or large skillet. Add enough water to cover the salmon halfway. Squeeze the lemon over the fish, then add the halves to the water. Sprinkle with salt and cover the skillet.
Cook over medium-low heat for about 10 minutes, until the center of the filet is cooked through.
Allow the salmon to rest, off the heat, for 10 minutes, then use 2 spatulas to carefully remove the fillet, cool, then refrigerate until serving.
Chive Yogurt Sauce
Add the chives, yogurt, milk and salt to a food processor. Process until smooth. Chill until serving. Cut and serve the salmon, spoon a generous portion of the sauce over each portion, garnish with more chopped chives and serve.
Allow the poached salmon and the sauce to come closer to room temperature (around 1 hour) before serving.