Sardine Recipe #3: Sardine-Tomato Sandwich. Slice a large garden tomato so you can use it like a cracker, sprinkle it with a bit of sea salt, and top it with a chunk of sardine, some mozzarella cheese, a sprig of fresh basil or sprinkling of basil spice (you could also use arugula, oregano or rosemary). For more carbs, you can add a rice or flax seed cracker under the tomato.