Heat the olive oil in a large sauté pan over medium heat. Add the butter and let it melt. Add the corn and cook for 5 to 7 minutes, stirring occasionally, until tender and lightly browned. Season with salt and pepper.
Transfer the corn to a large serving bowl and let cool slightly. Add the tomatoes, avocado, jalapeño and basil. Sprinkle with the feta, add the lime juice and a pinch of sea salt, then gently toss to combine. Serve immediately.
Let the corn lightly brown in the pan before stirring. Those caramelized edges bring out its natural sweetness and add deeper flavor to the salad.