¼cupplain Greek yogurt or another ¼ cup mayonnaise
Coarse salt and freshly ground black pepperto taste
Pinch cayenne pepper
Put the salmon in a large pot (you can cut salmon in two pieces for a big round pot), cover with cold water, add 2 teaspoons of salt, and bring to boil. Turn off the heat, and leave the salmon in the covered pot for 10 minutes.
Remove the fish from liquid and refrigerate until chilled (unless you want to serve it warm or rom temperature, in which case cool it until it is the temperature you want). If there was skin on the fillets, peel it off.
Meanwhile, in a food processor or blender, combine the cilantro leaves, shallots, and Dijon. Puree, add the mayonnaise and yogurt, if using, cream, salt, pepper, and cayenne and puree. Taste and adjust seasonings.
Serve the chilled fish with the sauce on the side.