Prep all ingredients ahead of time. Keep everything nearby to make things easy once the grill’s hot.
Preheat the side burner on your Weber Spirit Grill to medium heat.
Add butter to a cast-iron skillet. Once melted, stir in the elote seasoning.
Add the red onion, and sauté for 2 minutes until softened.
Add the corn and cherry tomatoes. Cook for 5–6 minutes until the tomatoes blister and the corn gets a bit charred.
Stir in the cotija cheese and cook for 1–2 more minutes, just until warm and slightly melty.
Transfer to a serving bowl, top with feta cheese, and sprinkle with more elote seasoning to taste.