Preheat grill to high heat. Lightly coat the ears of corn with canola oil or canola cooking spray Cook them on the grill until the slightly charred on all sides, this will take 10-12 minutes depending on the heat of your grill. Rotate the corn every 2-3 minutes.
Allow the corn to cool. Meanwhile, combine red onion, tomatoes, cilantro, lime juice, chili powder, cumin, taco seasoning, salt, jalapeno (if using) in a medium mixing bowl.
Once the corn is cool, remove kernels from the cob and add them to the mixing bowl, Toss all of the ingredients together. Next, add in the queso fresco cheese and toss to combine. Then stir in the sour cream until combined.
You can serve the salad right away or keep it covered in the refrigerator until you are ready to serve it. Just before serving, garnish it with the extra chopped cilantro and cheese. Serve it as a dip or as a taco filling. It's also delicious as a side dish for your favorite grilled meats or Mexican dishes.