Process red pepper, mayonnaise, lemon juice, and pepper in food processor or blender until smooth. Toss lettuce and onion with vinaigrette. Spread bread with red pepper mayonnaise. Arrange lamb on 2 slices bread; top with lettuce mixture and then remaining bread. Calories per serving 674, Prot 184 cal/46 g, Fat 378 cal/42 g, Carb 112, Sodium 576 mg lamb 04