Shuck the corn to remove all the silks. Baste with melted butter and place directly on the grill with a medium heat. Turn the corn every few minutes to make sure it is cooked evenly on all sides.
For Indoor cooking: Use an indoor grill or a griddle. If grilling, directions are the same as above. If using a stove top griddle, spray your griddle pan first so the corn won’t stick if using that cooking method. Cook on medium heat turning often.
Cook corn until kernels are slightly charred, rotating about one-quarter turn every couple of minutes until each side is done.
Grill the red onion while the corn is grilling. Turn them over once before removing from the grill. You want them just slightly heated with a few grill marks.
Remove the vegetables from heat and slice kernels from cob using a sharp knife.
Add the corn and onions to a large bowl then add the remaining ingredients. Toss to blend.
Serve immediately or refrigerate covered for later.