How to Make It
Heat broiler to high with the rack 6 inches from the flame.
Toss the Brussels sprouts, radishes, and apples in the oil on a rimmed baking sheet. Season with ½ teaspoon each salt and pepper.
Broil, stirring with a wooden spoon every 2 minutes, until the Brussels sprouts are charred and the radishes and apples are crisp-tender, 6 to 8 minutes. Sprinkle with the lemon juice and toss. Serve warm with the Parmesan.