Toss 1/2 thinly sliced small red onion with 3 tablespoons red wine vinegar; set aside 10 minutes. Stir in 2 tablespoons olive oil and 1 teaspoon each grainy mustard and honey. Grate 2 carrots and 1 beet on the large holes of a box grater; add to the dressing along with 1/2 thinly sliced small red cabbage and 1/2 cup parsley; season with salt and pepper. Let stand 20 minutes.
Photograph by Ryan Dausch