Prepare your grill. Grill the corn for 5 minutes over indirect heat until just cooked through. Don’t overdo it or it will become gummy. Alternatively, you can boil the corn for a few minutes. Cut the kernel from the ear of corn and place in a bowl. Add the tomato, pineapple, cilantro, juice from ½ lime (about 1 tablespoon), scallions, and salt to taste, about ½ teaspoon. Set aside.