Place the oil in a large skillet (cast iron is excellent for this) over high heat.
Once the oil is shimmering but not smoking, add the corn kernels in a single layer.
Let them cook undisturbed for a minute to get a good char, then stir.
Continue to cook, stirring occasionally, until the corn is lightly browned, about 5 minutes.
Remove the skillet from the heat. Immediately stir in the chopped red onion, bell pepper, chili powder, salt, and pepper, allowing the residual heat to soften them slightly.
Transfer the corn mixture to a large bowl and let it cool for a few minutes. Gently fold in the chopped tomato, avocado, lime juice, and cilantro.
Taste and adjust seasoning with more salt, pepper, or lime juice if needed.
Serve immediately.
Don't overcrowd the skillet when browning the corn.
Cook in batches if needed to ensure the kernels get a beautiful char rather than just steaming.
Add the avocado and cilantro just before serving to keep them from browning and wilting, ensuring the salad looks and tastes its freshest.
