How to Make It
Light a grill. In a medium bowl, gently mix the avocado with the cucumber, lime juice, minced jalapeño, cumin and the 1/4 cup of olive oil. Season the salsa with salt and pepper.
Brush the watermelon slabs with olive oil and season with salt and pepper. Grill over high heat, turning once, until nicely charred on both sides, about 4 minutes total. Transfer to a platter. Spoon the salsa on the watermelon and top with the cilantro leaves, dill sprigs and sliced jalapeño, if using. Serve right away.