WHAT is tuna suki?

"Tuna suki" is not a common culinary term. It's possible you meant one of the following:

1. Tuna Sashimi: This is a popular Japanese dish consisting of thinly sliced raw tuna served with soy sauce, wasabi, and pickled ginger.

2. Tuna Shabu-shabu: This is a Japanese hot pot dish where thinly sliced tuna is cooked in a simmering broth at the table.

3. Tuna Sukiyaki: This is a variation of the classic Japanese sukiyaki dish, featuring tuna as one of the main ingredients. It's cooked in a sweet soy sauce broth with vegetables and other ingredients.

4. Tuna Sushi: This is a common sushi variety where tuna is used as the main topping. It comes in various forms, including nigiri, maki, and temaki.

To help clarify what you meant, please provide more context or information about the dish you are referring to.