1. Place mustard seeds in a small saucepan over medium heat; cook, partially covered, for 2 minutes or until lightly toasted. Remove mustard seeds from pan. Add sugar and vinegar to pan; bring to a boil over high heat. Remove pan from heat; stir in mustard and salt. Combine mustard seeds, vinegar mixture, cabbage, bell pepper, and onions in a large bowl; toss well. Cover and chill 2 hours, stirring occasionally.