Chop ¾ of the salmon into ½-inch cubes and set aside. Cut the remaining salmon into large chunks and add to a food processor. Add the mustard, mayo, lemon juice and zest, and a couple shakes of cayenne to the food processor and puree into a paste.

In a large bowl, gently mix the paste, remaining salmon, scallions, 2 tablespoons panko, ½ teaspoon salt, and lots of freshly ground black pepper.

Line a sheet pan with parchment paper and lightly oil. Divide the salmon mixture into four portions and shape into patties. Cover and refrigerate for an hour.

Prepare your toppings in the meantime. Sprinkle the reserved panko onto a plate and press each patty into the panko. Heat canola oil in a heavy skillet over medium heat. Put two patties on the hot skillet at a time. Let cook until nicely browned, then flip. Cook until the burgers feel springy. Turn down the heat or take the skillet off the heat for a moment if the panko starts to burn. Transfer finished patties to a paper towel-lined plate and cook the next batch.

Top salmon burgers as you wish and enjoy!