I eat this for breakfast 2 or 3 times a week because it's so easy to make, incredibly healthy, and extremely cheap!
Simply toast the bread. Then put the raw tuna on that, with salsa drizzled on top. Takes about 3 minutes, and actually tastes really good. Make sure you're using natural/fresh/homemade salsa, and not that Ortega or restaurant style stuff. Those are loaded with sodium and weird ingredients you don't need.