01 - Preheat grill to medium-high heat. Lightly oil the grates to prevent sticking.
02 - Cut watermelon into rounds or wedges approximately 1-inch thick. Pat slices dry with paper towels to remove excess moisture.
03 - Place watermelon slices on preheated grill. Cook for 2-3 minutes per side until distinct grill marks appear and fruit is slightly charred but still firm. Remove and let cool slightly.
04 - In a small bowl, whisk together olive oil, balsamic glaze, Dijon mustard, honey if using, salt, and pepper until emulsified and smooth.
05 - In a large salad bowl, toss together arugula or baby greens, grilled watermelon cut into cubes or triangles, cherry tomatoes, and sliced red onion.
06 - Drizzle balsamic dressing over salad mixture. Use salad tongs to gently toss until all components are lightly coated.
07 - Top salad with crumbled feta cheese, fresh mint leaves, and toasted pumpkin seeds or pine nuts if desired. Serve immediately while watermelon is still slightly warm.