Preheat your grill to high heat until hot, and prepare your shucked corn on the cob.
Place the corn directly on the grill grates and cook, turning occasionally, until all sides are evenly charred and smoky, about 8-10 minutes.
Remove the corn from the grill and set it aside to cool just slightly—this helps handle it without burning your fingers.
In a bowl, whisk together mayonnaise, lime juice, and a pinch of chili powder to create a creamy, tangy sauce.
Use a basting brush or spoon to slather the mayonnaise mixture generously over each hot, charred ear of corn, ensuring it coats all sides evenly.
Sprinkle crumbled Cotija cheese generously over the coated corn, pressing it in slightly so it sticks.
Sprinkle chili powder over the cheese for a smoky heat and finish with a handful of chopped cilantro if desired.
Finish by brushing a little melted butter over the top for extra richness and a glossy finish.
Serve the street corn warm, with an extra squeeze of lime if you like more tang, and enjoy the smoky, crunchy texture with every bite.