Here are the main ingredients. Chop the onion into 5 mm wedges.
Heat the frying pan and sauté the onions with 1 tablespoon mayonnaise over medium heat.
When the onions are soft, add tuna without draining the soup. Add 1 tablespoon soy sauce.
Sauté until you can smell the rich aroma of soy sauce. Turn the heat off before anything burns.
Wash the potatoes and cover with plastic wrap. Microwave for 3 minutes at 600 W. Flip it over and microwave for another 2 minutes. Peel off the skin, chop into fourths and transfer into a bowl. Mix in the vinegar.
Combine ingredients from Step 4 with the potatoes. Add 1 tablespoon soy sauce and 1 tablespoon mayonnaise. Dish it up, top with sesame and pepper, and enjoy.
Here, I added some nanohana (rape blossoms) to add color.
I usually eat them warm, but one person commented that they're also good when chilled.
Story Behind this Recipe
I usually use onions and tuna because I like them stir-fried together. I thought it would be delicious if I used sweet onions and mixed fluffy spring potatoes with soy sauce. That's how it all came about.
I added the soy sauce in two batches to enjoy its flavor. I recommend you mix the potatoes when they're hot while making sure not to mash them too much. Please adjust the cooking time for the potatoes since it can vary according to size. You can boil or steam the potatoes instead of microwaving them.