In a large skillet, add grape seed oil and butter to the pan on medium heat. Add onions and garlic and sauté for 2 minutes until fragrant. Then add the corn and grape tomatoes to the skillet. Cook for 10 minutes.
While the corn is cooking mix together the salt, chili powder, cumin, and cayenne pepper. Coat the fish with half the spice mixture. Take the remaining spice mixture and sprinkle it over corn tomato mixture. Mix well then remove the corn and half the grape tomatoes from the skillet.
Place the fish in the skillet and cook for 5-7 minutes, turning halfway through. Remove the fish from the skillet and place the corn back into the skillet. Mix in cilantro and lime juice. Place fish on top of the corn mixture, and serve immediately.