Melt butter with 1/2 tbsp of olive oil in a large skillet on medium-high heat. Add the jalapeno, stir to coat, then saute for 1-2 minutes until it begins to char. Add the corn and the garlic and saute for 2-3 minutes.
Meanwhile, combine mayonnaise, chili powder, cilantro, lime zest, and juice from half the lime in a large bowl.
Add the corn to the bowl with the mayonnaise mixture, toss to combine. Then mix in the cotija cheese crumbles and cilantro. Squeeze the remaining lime juice over the corn and top with more cilantro and cotija cheese.