While the yeast is swelling, coarsely chop the onion and marinate it in any way convenient to you.
My favorite way is:
3 tablespoons soy sauce, a teaspoon with a hill of sugar, a tablespoon of rice vinegar. I heat it up in the microwave to a hot state so that the sugar dissolves. And pour out the onion.
As a result, it turns out crispy, with a pleasant caramel-soy flavor.