This quick, easy slaw combines juicy fennel, sweet apple, and tangy red onion. It makes a great side dish for barbecued meats or fish tacos. The slaw can be refrigerated, covered, for up to 4 hours before serving. Add the nuts at serving time so they don't get soggy.
Combine the fennel, apple, onions, and lemon juice in a medium-size bowl and toss to combine. Add the mayonnaise, yogurt, and salt and pepper to taste, and stir gently to coat the mixture. Stir in the nuts and fennel fronds, if using, just before serving.