Preparation

• Prepare a medium-high (400°F to 475°F) gas or charcoal grill fire. Grill the corn, turning occasionally, until the kernels are charred in places and crisp-tender, about 8 minutes. Cut the kernels from the cob.
• In a medium bowl, combine the lime juice, jalapeño, garlic, and 1/4 tsp. salt. Whisk in 2 tsp. of the oil, and season generously with black pepper. Stir in the corn, watermelon, onion, scallions, and basil; set aside.
• Brush the tuna with the remaining 1 Tbs. oil, and season generously with salt. Grill until done to your liking, 2 to 3 minutes per side for rare to medium rare. Serve with the salsa.