Heat the oil in a large skillet over medium-high heat. Add the corn to the skillet and cook for 4–5 minutes, stirring occasionally but not constantly, until lightly charred. Remove from the heat and cool for a few minutes.
Transfer the corn to a mixing bowl. Add the red onion, jalapeño, green onion, cilantro, and cotija cheese. Set aside.
In a small bowl, whisk together the sour cream, mayonnaise, lime zest, lime juice, cayenne pepper and chili powder. Season with salt and pepper to taste.
Pour the dressing over the corn mixture and toss to coat. Taste and adjust with more lime, salt, pepper, chili powder, or cotija if desired. Sprinkle with additional cilantro and cotija before serving.
Notes
Salad can be made up to 8 hours in advance and refrigerated in an airtight container.
Fresh corn gives the best flavor, but thawed frozen corn works well. If using canned corn, drain and pat dry before cooking.
Feta can be used instead of cotija.
For a milder salad, reduce the cayenne or omit the jalapeño.
For a tangier, lighter dressing, swap part of the sour cream or mayo with plain Greek yogurt.