Place one ear of corn at a time in the middle of a foil sheet.
Spread the butter or mayonnaise on top of the corn.
Sprinkle the top with a 1/2 teaspoon-1 teaspoon of chili powder.
Then sprinkle with 1 Tablespoon of Cotija cheese.
Top with just a small sprinkling of cilantro.
Tightly wrap the ear in a sheet of foil.
Repeat with each ear of corn.
Put 1/3 cup of water in the bottom of a slow cooker.
Place each foil-wrapped ear of corn into the slow cooker.
Cover and cook on high for 2 hours.
Remove the ears with tongs.
Open and sprinkle more Cotija cheese, salt to taste, and squeeze a bit of lime juice on top.