Place about one-quarter of the salmon in a food processor. Cover and process until mixture is blended and forms a paste, scraping down sides as needed. Add garlic and remaining salmon; cover and pulse until salmon is chopped and pieces are about 1/4-inch. Transfer to a bowl, and stir in breadcrumbs, lemon juice, relish, Dijon mustard, salt, and pepper. Gently shape mixture into 4 patties.
Heat a large nonstick skillet or griddle to medium-high heat; coat with cooking spray. Cook patties 2 to 3 minutes on each side or until a meat thermometer inserted into the center of a patty registers 145˚F.
Stir together mayonnaise, yogurt, mustard, lemon juice and zest and garlic powder in a small bowl.
Serve burgers on toasted English muffins with sauce and desired toppings.
Burger recipe method adapted from New York Times Cooking