1. Place caraway and fennel seeds in a mortar bowl or spice grinder; grind using a pestle or grinder until seeds become a medium powder. Combine pepper, vinegar, and crushed seeds in a small bowl; cover. Let stand 1 hour. Whisk in mayonnaise and sugar. Season with salt to taste.
2. Combine cabbage and next 3 ingredients in a large bowl. Add vinegar mixture, and toss until blended. Let stand 10 minutes to 1 hour before serving.