Place corn on a microwave-safe plate; cover tightly with plastic wrap. Microwave on high power until corn is fully cooked, 8 to 10 minutes. (Leaving plastic wrap in place, corn can be made up to 2 hours ahead.)
Mix sour cream, cilantro, chili powder, lime juice, salt and pepper. Cover and chill until ready to serve. (Makes 1/2 cup.)
About 10 minutes before serving time, heat butter in a 12-inch skillet over medium to medium-high heat. Add corn and cook, turning with kitchen tongs every few minutes, until golden brown, about 6 minutes. Serve immediately, with sour cream spread passed separately.