Remove the husks and silk from the corn. Pat the cobs dry, then rub lightly with neutral oil and season with kosher salt. The corn must be dry before grilling. Wet corn steams before it chars, which gives dull kernels instead of caramelised spots. A thoroughly dried cob is what allows the grill's direct heat to go straight into browning the kernel surface — any lingering moisture has to evaporate first, and that delay is exactly what produces pale, steamed-looking kernels instead of the deep blackened spots this dish is built around.

In a small bowl, mix the mayonnaise, Mexican crema or sour cream, lime juice, grated garlic, and salt until smooth. The mixture should be thick enough to cling to the corn, not runny. If it feels too stiff to spread, loosen with a few drops of lime juice. Do not make it thin, or it will slide off the hot corn. Combining mayonnaise with crema rather than using either alone balances two different textures — mayonnaise contributes body and cling, while the crema adds a lighter, tangier edge that keeps the coating from tasting flatly rich.

Combine the chilli powder, smoked paprika, and cayenne if using. Keep ready with the crumbled cotija before the corn comes off the grill. Having both the cheese and the chilli dust fully prepared and within reach before the corn is even off the heat matters for timing — the coating stage moves quickly while the corn is hot, and hunting for an ingredient mid-assembly risks the corn cooling before the cheese has a chance to properly cling.

Preheat a grill, grill pan, or cast-iron skillet over medium-high to high heat until very hot. Add the corn and cook for 10–12 minutes, rotating every 2 minutes, until the kernels are tender and charred in dark spots on all sides. Brush the corn with melted butter during the final 2 minutes of cooking. The butter should sizzle and help the kernels turn glossy and caramelised. Do not walk away from the corn. You want strong blackened spots, not fully burned rows of dry kernels. Rotating the corn every 2 minutes rather than leaving it in one position is what produces charred spots distributed across the whole cob instead of one heavily blackened side and three pale, under-cooked ones — the goal is even exposure to the direct heat all the way around.

Transfer the hot corn to a wooden board. While still hot, brush each cob generously with the creamy mayonnaise mixture, turning to coat the visible surface. The heat should slightly melt the coating into the kernels while leaving a visible creamy layer. Coating the corn while it's still genuinely hot, straight off the grill, is what lets the mayonnaise mixture soften and settle slightly into the charred kernel crevices rather than sitting as a stiff, separate layer on top — corn that's cooled even partway won't produce the same clinging, glossy coat.

Immediately scatter cotija heavily over each cob so it sticks to the creamy coating. Dust with the chilli mixture until visible red-orange speckles cover the cheese and corn. Working immediately after coating, while the creamy layer is still tacky, is what gives the cotija something to genuinely adhere to — cheese scattered over a coating that's already begun to firm up tends to fall away rather than cling evenly.

Scatter fresh cilantro over the corn and board. Serve with lime halves or wedges beside the cobs, cut-side up. Add extra cotija around the board if desired. Serve immediately while the corn is hot, the coating is creamy, and the cotija is still clinging to the charred kernels. Presenting the lime cut-side up rather than tucked to the side makes it immediately obvious and ready to squeeze, which matters here since the final squeeze of lime right before eating is what brightens the rich, creamy coating.