Combine and use to baste salmon then spread on buns, thin coating.
To make the burger mixture, thoroughly combine the burger ingredients in a medium bowl.
Divide into 4 portions, shape into patties 1/2 inch thick and 4 inches in diameter.
Heat the barbecue grill until the coals glow red with white ash around the edge.
The salmon patties are fragile, so handle them carefully; if you chill the patties on a plate in the refrigerator before putting them on the grill, they will hold together better.
When the barbecue is heated, put the salmon patties on the grill at least 2 inches apart.
Grill until the first side is nicely marked, about 2 minutes, then turn and baste with Lemon Sour Cream Butter.
Continue cooking until the burgers are just cooked through, about 2 minutes longer.
Split the buns and, if desired, butter lightly with Lemon Sour Cream Butter and toast them on the grill.
Spread the buns with mayonnaise or tartar sauce if using, add the burgers.