Trim and discard root ends and fronds from the fennel bulbs; cut the bulbs in half from root to tip. Cut the halves into 4 or 5 slices each, from root to tip.
In a large sauce pan, combine the sliced fennel, salt and about 1/2 inch of water; bring to a boil over medium-high heat. Cook, covered, until barely tender, about 3 minutes. Transfer the fennel to a colander to drain. Wipe out the pan and return to the heat. Add the butter and sugar; cook, over medium-high heat, until the butter is melted. Add the drained fennel. Reduce the medium; cook, turning, until nicely caramelized and browned, about 5 minutes. Transfer to a warm platter, sprinkle with salt and pepper. Serve immediately.
