Make cilantro sauce
In a small bowl stir together the mayonnaise, sour cream, lime juice, cilantro and garlic until combined. Cover and refrigerate until ready to use.
Cut the corn cobs
Heat oven to 400ºF (200ºC). Place a dish towel under a cutting board to keep it from slipping. Hold the corn cob on its end securely and use a sharp knife to make 4 vertical cuts into the corn cob so it breaks into 4 “ribs”.
Cook the corn cobs
Arrange the ribs in an even layer on a baking sheet and drizzle with the oil, turning to coat. Bake the corn until the kernels are tender and the corn is slightly charred, about 25 to 30 minutes.
Assemble and serve
Arrange on a serving platter and squeeze lime over the top. Season the corn with the Tajin and serve with the cilantro lime sauce.