Gather all of your ingredients.
Open the can of tuna.
Drain out the water.
My kitty loves tuna water so I always drain it into a bowl for him.
Add the mayonnaise. Some people like it dry while others prefer a more creamy consistency. Add the amount you desire.
Mix together the tuna and mayonnaise.
Cut the tomatoes in half. I have used grape tomatoes here, but cherry tomatoes are delicious too.
Place a dollop of tuna on one half.
Place the other half on the top. They are now ready to enjoy. My daughter loves this tasty snack.