Overnight Coleslaw with Mustard Seed

In a large, nonreactive mixing bowl, combine the cabbage, carrots and onion.

FOR THE DRESSING:
In a nonreactive saucepan over medium heat, mix the vinegar, oil, honey, lemon juice, mustard seeds, salt, and pepper. Bring to a boil, stirring often. Take the dressing off the heat; immediately pour it over the vegetables. Toss well, cover, and refrigerate for at least 6 hours (overnight is best) before serving.