1. Place spinach, fennel, apples, and fennel fronds in large bowl.

2. In small nonreactive bowl, combine lemon juice, shallot, mayonnaise, mustard, salt, and lemon zest. Whisk until mixture appears milky and no lumps remain. Place oil in liquid measuring cup so it is easy to pour. Whisking constantly, very slowly drizzle oil into mixture. If pools of oil gather on surface, stop addition of oil and whisk mixture well to combine, then resume whisking in oil in slow stream. Vinaigrette should be glossy and lightly thickened.

3. Pour dressing over spinach mixture and toss to coat. Serve immediately.

Serves 6 as a First Course