Easy Japanese-Style Whole Onion

Why not try making an impressive dish using a whole onion? Japanese-Style Whole Onion is a dish that allows you to fully enjoy the onion’s natural sweetness. It is incredibly easy to prepare, making it perfect for when you want a quick vegetable dish.

Japanese-Style Whole Onion is a simple yet flavorful dish made by microwaving a whole onion and drizzling it with seasonings like ponzu sauce or soy sauce. Onions are delicious whether simmered or roasted, but microwaving gives them a smooth, tender texture and brings out their natural sweetness. In this recipe, I sprinkle bonito flakes (katsuobushi) on top for an extra touch of Japanese flavor.

In modern Japanese households, the microwave is more than just a time-saver—it has become an everyday cooking tool. Using it to cook onions is also common, as simply microwaving them allows the onion’s natural moisture to steam it evenly throughout. Since some of that moisture evaporates during cooking, the flavor becomes more concentrated, resulting in a richer, sweeter taste.

Since the microwave does most of the work, your active cooking time is only a few minutes. This dish is easy to make, delicious, and visually appealing, making it well worth trying in your kitchen.

In Japan, it is quite common to cook vegetables in the microwave, but this practice may be unfamiliar in your countries. Even so, since there are several benefits to microwaving vegetables, I encourage you to give it a try in your everyday cooking. Some of the main benefits include:

• Quick cooking time
• Easy preparation
• Helps vegetables retain their shape
• Preserves more nutrients

Japanese-style whole onion is a perfect example of these benefits. Not only is it quick and easy to make, but it also helps the onion retain its shape while preserving its nutritional value.

Onions are particularly rich in nutrients like vitamin C, potassium, and allyl sulfides. These are water-soluble nutrients that tend to be lost during regular cooking, but microwaving, which doesn't require water or oil, helps preserve them. In other words, if you want to get the most out of the onion’s health benefits, microwaving is actually an ideal method.

That said, there is one thing to watch out for: if the microwave power is too high, the onion could burst. To prevent this, be sure to set the microwave to medium power (500-600W). Follow this guideline to cook safely and enjoy this delicious, nutritious onion dish.

When making this dish, there is one simple trick you should try before microwaving an onion: make a cross-shaped cut in it. This cut makes the onion much easier to eat.

It is easy to do—after peeling the onion and trimming both ends, simply make a cross-shaped incision on the top with a knife. The cut should go about halfway down into the onion. Be careful not to cut too deeply, as the onion might fall apart while microwaving.

The seasoning for this dish is simple—just drizzle it with ponzu or soy sauce.

If you prefer a slightly tangy flavor, go with ponzu; otherwise, soy sauce works well. However, I personally find that using only one of them feels a bit lacking, so in this recipe, I combine both in a 1:1 ratio. Feel free to use whichever you like.

In Japan, it is also common to add butter or Japanese mayonnaise to these seasonings. This adds richness and makes the dish even milder, so if you are curious, give it a try.

Ingredients

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Instructions

🕒 Total: 7 mins mins

Step 1
Peel the onion and trim off both ends. Make a cross-shaped incision on the top, cutting about halfway down into it.

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Step 2
Place the onion in a microwave-safe container and loosely cover it with plastic wrap. Microwave on medium power (500-600W) for 4-5 minutes, or until heated through.

If the onion weighs more or less than 7-11 oz (200-300 g), adjust the cooking time accordingly. Do not exceed medium power (500-600W), as the onion may burst in the microwave.

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Step 3
Carefully remove the container from the microwave and take off the plastic wrap. Drizzle the onion with ponzu sauce and soy sauce (or double the amount of either one). Sprinkle shaved bonito flakes on top to taste.

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To store

You can store it in the refrigerator for up to 2 days.