Directions

1. Heat butter over medium heat in a large heavy-bottomed frying pan. Add bell peppers and onion and cook, stirring occasionally until vegetables are soft, 7-8 minutes. Transfer to a plate and set aside.
2. Cut three-quarters of the salmon into ¼-inch dice and place in a medium bowl. Cut remaining salmon into 1-inch pieces and add to a food processor with mustard, 1 tablespoon mayonnaise, the lemon juice, and lemon zest. Pulse ingredients into a paste, then transfer to bowl containing the 1/4-inch salmon pieces.
3. Add 2 tablespoons of panko breadcrumbs, the cooked onion mixture, and Cajun seasoning; mix gently until combined. Form 4 equal-size salmon patties about 4 inches wide, using a 4-inch metal ring if you like for even shaping. Pour remaining panko onto a plate. Turn patties in panko to coat. Place on a plate or a sheet pan lined with parchment paper. Refrigerate patties at least 30 minutes or up to 1 hour.