In a sizable mixing bowl, combine the mayonnaise, egg, Dijon mustard, Worcestershire sauce, Old Bay seasoning, garlic powder, paprika, salt, and pepper. Whisk until smooth and fully incorporated.
Add the crab meat, half of the breadcrumbs, chopped scallions, diced bell pepper, and parsley. Gently fold everything together, taking care not to break up the crab pieces.
Portion the mixture into six uniform mounds, then shape each into a round patty. Press each one lightly into the remaining breadcrumbs to coat.
Transfer the shaped crab cakes onto a tray or plate and refrigerate for 15 to 20 minutes to help them firm up.
Warm the butter in a large skillet set over medium heat. Once hot, cook the crab cakes for 3 to 4 minutes per side, or until each is deeply golden and crisp.
Move the cooked cakes to a serving platter. Finish with a squeeze of fresh lemon and serve alongside tartar sauce or remoulade.