Heat avocado oil in a large nonstick skillet over high heat.
Add corn, season lightly with kosher salt, and cook without stirring until charred on one side (~2 minutes).
Toss corn and cook until charred on the next side (~2 minutes more).
Continue tossing and charring, rotating corn until it’s well charred all over (~10 minutes total). Transfer to a large bowl.
Add cotija cheese, scallions, cilantro, jalapeño, garlic, mayonnaise, lime juice, and chile powder. Toss thoroughly to combine.
Adjust seasoning with salt and chile powder to taste. Serve immediately.