While your grill preheats to medium-high heat, prepare all your fresh ingredients for efficient assembly. Dice the onion into small, uniform 1/4-inch pieces and set aside. Seed and dice the roma tomatoes, removing excess liquid to prevent a watery salsa. Seed and mince the serrano pepper, adjusting the amount based on your heat preference. Chop the fresh cilantro and set everything in separate small bowls—this mise en place will make the final assembly quick and easy.

Place the shucked corn directly on the grill grates over medium-high heat and grill for 2-3 minutes, rotating occasionally until all sides develop dark char marks. This charring is crucial—it caramelizes the corn's natural sugars and adds a smoky depth that makes this salsa exceptional. Once charred, transfer the corn to a cutting board and let it cool just enough to handle, about 2-3 minutes.

Using a sharp knife, carefully cut the corn kernels off the cob by standing the ear upright and slicing downward, rotating as you go. I like to place the cob in a shallow bowl to catch all the kernels and any flavorful juices they release. Transfer the cut corn to a medium mixing bowl, being sure to pour in any accumulated juices.

Add the prepared onion, tomatoes, serrano pepper, cilantro, and ground cumin to the bowl with the corn. Drizzle the extra virgin olive oil over everything and squeeze in the fresh lime juice. Gently fold all ingredients together until evenly combined, then season with salt and black pepper, tasting as you go. I always add the salt gradually because the lime juice's acidity can affect how much salt you'll actually need for the best flavor balance.

Let the salsa rest at room temperature for 10-15 minutes so the flavors can meld together, or refrigerate for up to 2 hours if you prefer it cold. Give it a gentle stir before serving alongside grilled proteins, as a topping for tacos, or with tortilla chips.