Heat vegetable oil in a heavy skillet over medium-high heat until shimmering.
Add the corn kernels to the skillet in a single layer and cook undisturbed for 2-3 minutes to achieve a char.
Stir the corn and continue cooking for an additional 3-4 minutes until golden brown; remove from heat and allow to cool completely.
In a large mixing bowl, whisk together mayonnaise, sour cream, lime juice, chili powder, and smoked paprika until the dressing is emulsified.
Add the cooled charred corn, diced cucumber, red onion, and cilantro to the mixing bowl.
Toss the ingredients thoroughly with a spatula to ensure even distribution of the dressing.
Gently fold in the crumbled Cotija cheese to maintain its texture.
Adjust seasoning with salt and pepper to taste, then refrigerate for at least 30 minutes before serving to allow flavors to integrate.