If using fresh corn, grill the corn on medium-high heat for about 10 minutes, turning occasionally until charred. Allow to cool, then cut the kernels off the cob. If using frozen corn, cook according to package instructions and let cool. For canned corn, drain and rinse before using.

In a large mixing bowl, combine the corn kernels, diced red onion, diced red bell pepper, crumbled feta cheese, and chopped cilantro.

In a separate small bowl, whisk together the mayonnaise, sour cream, lime juice, chili powder, garlic powder, salt, and pepper until smooth.

Pour the dressing over the corn mixture and gently toss until everything is well coated.

Taste and adjust seasoning if necessary. Chill in the refrigerator for at least 30 minutes before serving to allow flavors to meld.