Thinly slice 4 lemon wheels from the lemon, then add them right on the baking sheet.
Broil for 3 minutes (for optimal charring, place the tray about 4-5 inches from the heat source). Remove the tray and stir. Then broil 2 to 3 minutes more, until the spears are tender when pierced by a fork at the thickest part. Sprinkle with grated Parmesan cheese (optional) and serve.