1 large fennel bulb, cored and very thinly sliced, 2 cups (fronds reserved)
1 large organic red apple, such as Fuji or Gala, unpeeled, ( coarsely grated)
1 small red onion very thinly sliced (1/2 cup)
2 teaspoons fresh lemon juice
2 tablespoons mayonnaise
1 tablespoon plain yogurt