Carefully cut the kernels off the cobs. Side Note: I put a coffee cup upside down in a large bowl and placed the cob on top of the mug, which makes it easier to cut the kernels this way without making a big mess.
Heat the butter in a large skillet over medium heat. Add the diced onion and cook, stirring often, for 2 minutes.
Add the corn kernels, tomatoes, sea salt, and freshly cracked black pepper to taste, and cook, stirring gently, for 3-4 minutes.
Add the garlic and cook, stirring constantly for 1 minute.
Pour into a serving bowl and top with feta and basil. Serve and enjoy.