Remove the skin and any bones from the salmon filet. Place ¼ of the salmon in a food processor and process until almost paste-like. Finely chop the remaining salmon. Combine all of the salmon with the yellow pepper, garlic, scallions, egg, breadcrumbs, soy sauce, and lemon juice. Shape into 4 patties.
Heat a grill pan or skillet over medium-high heat until a drop of water sizzles immediately when splashed on the pan. Spray with cooking spray and cook the patties for 4-5 minutes per side.
Combine the mayonnaise and Sriracha and mix well.
Serve the salmon burgers on a bed of arugula (or on buns if desired) with a dollop of spicy mayo.