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. -- Arrange the fennel salad on four individual plates. Shave the pecorino in long shards over each plate, and serve.