Combine the mayonnaise, Dijon mustard, egg, cayenne pepper, salt and pepper in a large bowl. Stir in sautéed onions and celery. Gently fold in the lump crabmeat and 2 tablespoons of panko breadcrumbs. Stir carefully so you don’t break up all the crab pieces.
Pre-heat a non-stick skillet over medium heat.
Add a tablespoon of olive oil to the skillet and gently place the crab cakes into the pan. Cook for about 4 to 5 minutes per side, until the crumbs are nicely browned and the cake is cooked through. Serve the crab cakes with tartar sauce or cocktail sauce, or dress it up with a little sherry sauce.