- 1 small red onion, thinly sliced
 - 1 tablespoon plus 1 teaspoon Dijon mustard
 - 2 teaspoons finely grated fresh orange zest
 - 4 1/2 tablespoons fresh orange juice
 - 1/3 cup olive oil
 - 2 heads radicchio (3/4 pound total), cored and coarsely chopped
 - 1/2 small head red cabbage, cored and coarsely chopped
 - 2 pints cherry tomatoes, halved
 - 1/2 teaspoon sugar, or to taste
 
- Soak onion in cold water to cover 15 minutes.
 - Whisk together mustard, zest, juice, and salt and pepper to taste. Add oil in a slow stream, whisking until emulsified.
 - Drain onion well and toss together with radicchio, cabbage, tomatoes, and enough dressing to coat. Toss salad with sugar and salt and pepper to taste.