Use a sharp knife and cutting board to cut the watermelon into four 1-inch thick slices. Remove any seeds if present.
Brush both sides of each watermelon slice with olive oil using a basting brush or spoon to prevent sticking and enhance caramelization.
1 large watermelon
Preheat the grill to high heat (about 450-500°F). Place the watermelon slices directly on the grill grates, positioning them to achieve prominent grill marks.
Grill the watermelon slices for about 2-3 minutes per side, until distinct grill lines form and the surface begins to caramelize with a slight charring. Use tongs to flip, ensuring even browning.
Remove the slices from the grill once evenly charred and slightly softened, with a fragrant smoky aroma emanating. Let rest for 1 minute before serving.
Optional: season with salt and black pepper to taste, then serve immediately for a smoky, caramelized fruit experience.
1 large watermelon