Stove Top Method: Remove husks from corn. Cut kernels from the cob over a Bundt pan. Heat vegetable oil in a large skillet over medium-high heat until shimmering. Add corn, cook, tossing occasionally, until corn is charred all over (about 8-10 minutes). Remove from heat and allow to cool.
Outdoor Grill Method: Remove husks from the corn. Heat grill to medium. Grill corn (8-10 minutes), turning frequently, until corn is charred all over. Remove from heat and allow to cool. Cut kernels from the cob over a Bundt pan.
In a large bowl, toss chopped avocado with 1/2 tablespoon lime juice. Add cooled corn, black beans, onions, cilantro, jalapeno, and garlic.
In a small bowl, combine mayonnaise, 1 tablespoon lime juice, chili powder, and smoked paprika, stir until well combined. Pour dressing over corn salad. Gently toss everything together.
Arrange chopped lettuce on a serving platter. Spoon corn salad over lettuce. Sprinkle Cotija cheese over all, and serve.