Ingredients

• 1 red onion
• 3 tablespoons cider vinegar
• 1 1/2 teaspoons sugar
• 1 teaspoon powdered mustard or 2 teaspoons Dijon mustard
• 1/2 cup extra-virgin olive oil
• 1 pint vine-ripened cherry tomatoes
• 4 cups mixed crunchy sprouts* such as pea and lentil
• 3/4 pound baby spinach
• *available at specialty produce markets and some natural foods stores and supermarkets

Instructions

1. Halve onion lengthwise and very thinly slice crosswise. In a bowl cover onion with cold water. Chill onion in water 30 minutes.
2. Make dressing while onion is chilling In a bowl whisk together vinegar, sugar, mustard, and salt and pepper to taste and add oil in a slow stream, whisking until emulsified. Dressing may be made 2 days ahead and chilled, covered. Drain onion well in a colander and pat dry. Quarter tomatoes and in a large bowl toss with onion, sprouts, spinach, and dressing.
3. In a bowl whisk together vinegar, sugar, mustard, and salt and pepper to taste and add oil in a slow stream, whisking until emulsified. Dressing may be made 2 days ahead and chilled, covered.
4. Drain onion well in a colander and pat dry. Quarter tomatoes and in a large bowl toss with onion, sprouts, spinach, and dressing.