If using fresh corn, grill the ears over medium heat for about 10 minutes, turning occasionally until they are charred. Allow the corn to cool, then cut the kernels off the cob.
In a large mixing bowl, combine the diced cucumber, cherry tomatoes, and red onion.
In a separate bowl, whisk together the mayonnaise, sour cream, lime juice, chili powder, garlic powder, salt, and pepper until smooth.
Pour the creamy dressing over the vegetable mixture and toss gently to coat all ingredients evenly.
Add in the grilled corn kernels and toss again.
Taste and adjust seasoning as needed, adding more salt, pepper, or lime juice to your preference.
Transfer the salad to a serving dish and garnish with chopped cilantro and crumbled feta cheese, if desired.
This salad can be served immediately or chilled in the refrigerator for 30 minutes for a cooler option.
Leftovers can be stored in an airtight container in the refrigerator for up to 2 days.