In a large pot, bring 4 quarts water to boil. Add corn and boil until bright yellow and tender, about 4 minutes. Set aside to cool slightly, then skewer with sticks if desired.
Rub an ear of corn with half a lime, then coat with 2 tablespoons mayonnaise (a spatula works well).
Coat with 2 tablespoons Parmesan cheese and season with Tajin or chile powder to taste (I like about 1 teaspoon Tajin). Repeat with remaining ears of corn.
Parmesan: Look for the grated Parm in the green shaker can. This might sound inauthentic, but it is closest to what street vendors actually use in the non-touristy parts of Mexico. Or, substitute Cotjia cheese or feta cheese.
Tajin seasoning: Tajin is a mild chili powder with a bright lime flavor that tastes great on Elote. Or, try regular chili powder, ancho chile powder, or even cayenne pepper (if you love the heat).
Yield: This recipe makes 4 tasty ears of corn. The recipe can easily be doubled or tripled.
Storage: Store leftovers covered in the refrigerator for up to 4 days.
Grilling: To grill the corn instead of boiling it, leave it in the husk. Preheat a grill over medium-high and clean and oil grilling grate. Place corn over direct heat and cook, rotating occasionally, until cooked through and charred in spots on all sides, about 8 minutes total.