Finely chop the salmon into tiny pieces. Add to a large mixing bowl. Finely chop the sweet peppers and scallions. Add to the mixing bowl with salmon. Add panko breadcrumbs, egg whites, lemon juice, lemon zest, salt and pepper to salmon. Using hands, mix until well combined. Using hands and a third-cup measuring cup as a mold, form the salmon mixture into 10 patties and set aside. Heat a large nonstick pan over medium-high heat and spray with cooking spray. Cook salmon patties for 3 to 4 minutes per side until cooked through and browned. Spread mayonnaise onto rolls, add salmon patty and top with baby arugula.