Soak ½ cup of finely chopped red onion in cold water for 10 minutes. Drain and pat dry.
In a large bowl, whisk ½ cup of mayonnaise, ¼ cup of sour cream, the zest of 1 lemon, 1 tablespoon of lemon juice, 1½ teaspoons of honey, ½ teaspoon of salt, and ¼ teaspoon of black pepper.
Cut 3 cored tart-sweet apples into ½in / 1cm pieces. Toss them in the dressing with 1½ cups of thinly sliced celery, 1 cup of halved grapes, and the onion.
Before serving, stir in 1 cup of toasted, chopped walnuts and 1 tablespoon of finely chopped chives.
