For the burgers: Cut parchment or waxed paper into four 6-inch squares. Chop the scallions in a food processor. Add the salmon, lemon zest and juice, and pulse until finely chopped, with some small pieces remaining. Divide the salmon into four mounds on the parchment squares. Shape the salmon into patties, about 4 1/2-inches wide, being mindful not to over handle. Either cook right away or cover and refrigerate the burgers for a few hours before cooking.
When ready to cook, preheat grill to medium heat, 375 to 400 degrees F.
Sprinkle the tops of the burgers with salt and pepper. Grease the preheated grill with oil and carefully flip the burgers onto the grill, parchment-side up. Peel off the parchment and sprinkle the other side of burgers with salt and pepper. Cook until the centers begin to turn pale pink and the burgers release from the grill, about 5 minutes. Flip and cook through, about 3 minutes. For the mayonnaise: Combine the mayonnaise and Sriracha.
Serve the burgers in buns or lettuce wraps. Top with the mayonnaise and serve with the lemon wedges.
These burgers flip more easily when chilled at least 15 minutes before cooking, but it isn't necessary if you take extra care in releasing the patties from the grill grates. For easier flipping, hold the spatula handle perpendicular to the grill grates, so that the spatula blade edge is parallel to the grates, then lift gently.