01 - Bring a large pot of salted water to a rolling boil. Add fusilli or rotini pasta and cook according to package directions until al dente. Drain thoroughly and rinse under cold running water to halt cooking. Set aside to cool completely.
02 - Preheat a grill or grill pan to high heat. Place corn ears directly on the grate and grill for 8–10 minutes, rotating every couple of minutes, until kernels are lightly charred and blistered on all sides. Let cool, then stand each ear upright and slice kernels from the cob. If using frozen corn, sauté in a dry skillet over high heat until golden and slightly charred.
03 - In a large mixing bowl, whisk together mayonnaise, sour cream, lime zest, lime juice, chili powder, smoked paprika, cayenne pepper (if using), sea salt, and ground black pepper until smooth and well combined.
04 - Add the cooled pasta, grilled corn kernels, diced red bell pepper, finely diced red onion, sliced green onions, and chopped cilantro to the dressing. Toss vigorously until every component is evenly coated.
05 - Gently fold in the crumbled cotija cheese, diced jalapeño, and avocado if using, taking care not to break up the cheese crumbles or mash the avocado.
06 - Cover and refrigerate for at least 30 minutes to allow the flavors to meld. Taste before serving and adjust salt, pepper, or lime juice as needed.