Position an oven rack in the top third of the oven and preheat the broiler to high.
Place the whole poblano pepper on a baking sheet. Broil for 5 to 7 minutes, turning occasionally with tongs until the skin is charred and blistered on all sides.
Transfer the charred pepper to a bowl and cover tightly with plastic wrap or a lid. Allow it to steam for 10 minutes to loosen the skin.
Peel the charred skin off the poblano and discard. Remove the stem and seeds, then finely dice the flesh.
In a medium mixing bowl, combine the lime juice, lemon juice, salt, diced red onion, and diced jalapeños. Let macerate for 5 minutes to mellow the raw onion bite.
Add the thawed white corn, diced roasted poblano, and chopped cilantro to the bowl.
Toss all ingredients thoroughly until the corn is evenly coated in the citrus dressing.
Refrigerate for at least 30 minutes before serving to allow the flavors to marinate.