Here in Spain we eat a lot of "bocadillos" (sub style sandwiches). The tuna and tomato one is popular, and my kids like it. I normally buy canned tuna and comes in oil (vegetable or olive). Although I like tuna, I don't digest it very well. However, the other day natural canned tuna was on sale and I bought it. In the blender I chopped some fresh tomatoes, added the tuna and some olive oil. It is good, natural, and a great source of protein (read the can). It's delicious to put over toast or on some good crusty bread. And it is not aggressive to my stomach!