Start by placing your fresh salmon filet, Dijon mustard, mayonnaise, shallot, capers, lemon juice, dill, salt, pepper, and optional cayenne into a food processor. Pulse until the mixture is coarsely ground, ensuring not to purée it.

Transfer the salmon mixture into a mixing bowl and gently fold in the breadcrumbs until well combined. Mold into four patties, each about ½ to ¾ inch thick.

Place your formed patties on a plate or tray and cover them lightly with plastic wrap. Refrigerate for 15 to 20 minutes.

While your patties chill, prepare the creamy herb aioli by combining mayonnaise, grated garlic, lemon juice, capers, dill, and scallions in a small bowl. Mix well and refrigerate.

Cook your salmon burgers by preheating your grill to medium-high or heating oil in a skillet over medium heat. Cook patties for about 4 minutes on each side, or until golden brown and cooked through.

To assemble, start with a toasted burger bun or lettuce leaves, place the cooked salmon patty on top, generously spread herb aioli and add desired toppings.