Sauté diced onions and bell pepper with pinch of salt until browned and moisture evaporates, about 5-7 minutes. You want the color to be browned, not just translucent. Once browned, allow to cool completely.
Mix cooled vegetables with ground turkey, Worcestershire sauce, mayo, black pepper, thyme, bread crumbs, and egg until well combined.
Form into 9-10 patties (about 5 oz each).
Refrigerate patties at least 2 hours or overnight.
Heat grill to 400°F.
Season patties with seasoned salt and brush lightly with neutral oil before grilling (both sides).
Grill 5-6 minutes per side until internal temperature reaches 165°F.
Rest 5 minutes before serving.