In a 10- to 12-inch frying pan over medium-high heat, stir onion in olive oil until limp, 5 to 7 minutes. Add corn and stir often just until tender to bite, 5 to 6 minutes.
Pour mixture into a wide serving bowl and stir in tomatoes, basil, and vinegar. Add salt and pepper to taste.
Sprinkle goat cheese over salad; serve warm or at room temperature.
Cutting kernels: An average ear of corn weighs from 10 to 14 ounces and yields about 1 cup of kernels. To remove them, with a large, sharp knife, cut off and discard the stem end of each ear down to the beginning of the kernels. Pull off and discard the husks and silks; rinse ears. Holding each ear upright, shear off the kernels close to the cob.