If the pot seems too dry, add 1 tablespoon of oil and keep the heat on medium. Add the Vidalia onion and cook, stirring often, until well browned, about 10-15 minutes. Remove and transfer to a bowl. Turn the heat to medium-high and add the tomatoes, cut side down, and cook without moving for 5-8 minutes or until charred. Transfer the tomatoes to the bowl with the onions.