Preheat oven to 500°. Line a rimmed baking sheet with aluminum foil.
Place corn and peppers on prepared pan. Bake 25 minutes, or until corn and peppers appear blistered; stir corn halfway through cooking time. Place peppers in a re-sealable plastic bag: seal, and let stand 10 minutes to loosen skins. Remove skins from peppers and chop. Cool corn and peppers completely.
In a medium bowl, combine corn, peppers, and green onion.
In a separate bowl, combine sour cream, mayonnaise, lime juice, chipotle pepper, salt, and chili powder.
Combine sour cream mixture with corn mixture. Garnish with green onion, if desired. Cover and chill.
