Bring a large pot of water to a boil. Add the corn and cook until just tender, about 5 minutes. Drain and rinse in cold water just until cool enough to handle.
Slice the kernels off the cobs and place them in a large bowl. Add the tomatoes, onion, jalapeño, cilantro, lime juice, minced garlic, cumin, garlic powder, and onion powder. Add the salt and chili powder, if using.
