Put the salmon in a food processor and pulse about 6 times, just until it is finely chopped. Stop before you have a paste! Can chop with a French Chef's knife.
Put the yogurt, scallions, dill, mustard and the capers into a large bowl and stir to blend.
Finely grate the zest of the lemon into the bowl.
Stir in the salmon, gently
Season with salt
Taste for flavor and maybe squeeze some lemon juice into the mix.
Cover the bowl, pressing the plastic wrap or wax paper against the surface of the mix, and refrigerate for at least 2 hours ( the burger mix may be refrigerated for up to 8 hours.)
To make the burgers, divide the salmon into 6 portions and shape each one into a patty. Lightly coat a grill pan or skillet with a small amount of oil or spray and place it over medium-high heat. Cook the burgers in two batches, don't crowd the pan for about 2 minutes on each side - you want to crisp the exterior and just warm the insides. Wrap the salmon sandwich with double aluminum foil, pack in an insulated cooler or serve at room temperature or chilled. This salmon burger tastes great either warm or chilled. Serve with the toppings you like,