01 - Bring a large pot of salted water to a boil. Cook fusilli or rotini according to package directions until al dente. Drain well 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, turning occasionally, until kernels are lightly charred and smoky. 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 edges begin to blacken.
03 - In a large mixing bowl, whisk together mayonnaise, sour cream, lime zest, lime juice, chili powder, smoked paprika, cayenne pepper (if desired), sea salt, and black pepper until smooth and fully combined.
04 - Add the cooled pasta, grilled corn kernels, diced red bell pepper, red onion, green onions, and chopped cilantro to the dressing. Toss thoroughly, ensuring every ingredient is evenly coated.
05 - Gently fold in crumbled cotija cheese. If using, add the diced jalapeño and avocado, folding with care to keep avocado pieces intact.
06 - Cover and refrigerate for at least 30 minutes to allow flavors to develop. Taste before serving and adjust salt, pepper, or lime juice as needed.