Tuna Mayo Don is just Tuna Mayo on rice. Don is short for donburi which means bowl. Donburi are rice meals served in bowls which may have toppings like beef, chicken, pork etc. I just learned of this dish after watching Midnight Diner (Shinya Shokudo Season 2) a Japanese drama series now serialized on Netflix.
If you love tuna onigriri then you will love tuna mayo don. It does not really require cooking except for making your rice.
Drain a small can of tuna (I like to use this Korean brand), or you can use any brand of albacore tuna. Then add 1 tsp miso, 2-3 tbsp. Japanese Mayo and 1 tbsp. minced onion (optional). Mix everything together.
Scoop some hot cooked white rice into a bowl. Place 3-4 tbsp of your tuna on top of your rice and garnish with some nori strips or furikake.
I made an updated version of tuna mayo don by adding diced avocados. It makes the dish more appealing and gives a better mouth feel to it. Next time I will try adding ingredients like cucumbers, mango and tobiko.