Tuna Melt Stuffed Tomatoes. Grain free, primal, gluten free and low carb.   Tuna Melt Stuffed Tomatoes are a grain free, primal, low carb tuna melt without the bun and the carbs. Hollowed out tomato halves filled with tuna salad and topped with melted cheese. These are an easy, high protein, low carb alternative to