1. Using a mandoline or other vegetable slicer, shave the fennel crosswise into 1/3-inch-thick slices. Place in a bowl and toss with the lemon juice and olive oil. Add the blood orange segments, pomegranate seeds, and fennel fronds and toss gently to mix. Season with salt and pepper.
2. Arrange the fennel salad on four individual plates. Shave the pecorino in long shards over each plate, and serve.