Prepare the corn by boiling fresh ears for 5 minutes and cutting the kernels off.
In a large bowl, combine the corn, diced red and green bell peppers, and chopped red onion.
Add chopped cilantro to the bowl.
In a separate bowl, whisk mayonnaise, sour cream, lime juice, salt, and pepper.
Mix in chili powder if desired.
Pour the dressing over the corn mixture and gently stir to combine.
Taste and adjust seasoning with more salt, pepper, or lime juice.
Cover the salad and refrigerate for at least 30 minutes.
Stir again before serving and garnish with cilantro if desired.
Serve chilled or at room temperature.