Preheat grill. Rub chicken with olive oil and season with salt and pepper. Grill chicken for 3-4 minutes until done.
Slice lemon in half and place cut side down on the grill until marked.
In a skillet over medium-high heat, saut onions and garlic in olive oil. Add corn and tomatoes and cook about a minute or until tender. Toss with butter, lemon juice and basil, and season with salt and pepper.
Place corn salad on the plate and top with chicken.