How to Make It
Preheat grill to high (about 500°F).
Slice watermelon crosswise into 5 (1 1/2-inch-thick) slices. Cut each slice into quarters to make 20 wedges. Grate 2 tablespoons lemon rind from lemons; set aside. Slice lemons into 1/2-inch-thick slices.
Add watermelon wedges and lemon slices to grill grate; grill 1 minute on each side or until nicely charred. Place watermelon on a serving platter. Squeeze juice from a few charred lemon slices over watermelon; add remaining slices to platter. Sprinkle watermelon evenly with salt, chile powder, and lemon rind.