To prepare mayonnaise, cut bell pepper in half lengthwise; discard seeds and membranes. Place pepper halves, skin sides up, on a foil-lined baking sheet; flatten with hand. Broil 12 minutes or until blackened. Place in a zip-top plastic bag; seal. Let stand 10 minutes. Peel pepper. Place pepper, 1/3 cup mayonnaise, garlic, and hot pepper sauce in a food processor. Process until smooth; transfer to a bowl, and chill.
To prepare crab cakes, combine 1/3 cup mayonnaise and next 6 ingredients (through crab) and 3/4 cup panko in a large bowl; stir until well combined. Form into 6 patties; dredge patties in remaining 1/2 cup panko. Heat 1 tablespoon butter in a large nonstick skillet over medium-high heat. Add 3 patties to pan; cook 10 minutes or until lightly browned and cooked through, turning once. Remove from pan, and keep warm. Repeat procedure with remaining butter and patties. Serve crab cakes with watercress and red pepper mayonnaise. Garnish with lemon wedges, if desired.
Wine note: The sweet, succulent flavor of crab is lovely with a crisp, dry white that's clean and pure tasting. One of my favorites is albariño from the northwestern corner of Spain. Nora Albariño 2004 from Rias Baxais ($16) is zesty, with a hint of citrus, starfruit, and dried peach. -Karen MacNeil