Name: Classic Italian Sweet and Sour Red Onions
Prep time: 10 min
Cook time: 10 min
Total time: 20 min
Ingredients: 500 g red onions (- 1.1 pound); 50 ml white wine vinegar (- 3 ⅓ tablespoons); 50 g granulated sugar (- ¼ cup); salt (- a pinch); 4 tablespoons olive oil (- extra virgin)

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Sweet and sour red onions, especially those from Tropea in the Calabria region, are a true Italian classic. While Tropea onions are renowned for their flavor, you can easily use any red onions if you don’t have access to them.

This dish is incredibly versatile and pairs beautifully with bread, bruschetta, cold cuts, cheeses, or as a filling for focaccia, piadina, and even pizza. Whether served as an appetizer, alongside a main course, or as part of an aperitif, these caramelized onions are a hit!

One of the best things about this recipe is that it’s delicious whether served hot or cold. The preparation is simple: the onions are cooked in a mixture of oil, vinegar, and sugar.

You can adjust the cooking time depending on how you like your onions—shorter for a crispier texture or longer for a softer, melt-in-your-mouth experience.

The color of your onions will vary depending on the season—spring onions give a delicate pink hue, while summer onions produce a more vibrant color.

No matter how you prepare them, these sweet and sour red onions are a must-try!

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Ingredients
Instructions
Storage
Tips and Variations
How to Serve
Curiosities
Recipe Card

Ingredients

Prep Time: 10 Min | Cook Time: 8-10 Min | Servings: 4

500 g (1.1 pound) of red onions. I used Tropea red onions, renowned for their flavor, but you can easily use any red onions if you don’t have access to them.
50 ml (3 ⅓ tablespoons) of white wine vinegar
50 g (¼ cup) of granulated sugar
a pinch of salt
4 tablespoons of extra virgin olive oil

Instructions

Prepare the Onions

Step 1) - Start by cleaning the onions. Remove the outer skin and cut off the tough ends. Once the onions are cleaned, place them on a cutting board and use a sharp knife to slice them. It’s important that the slices aren’t too thin, so avoid using a mandoline for this step. The ideal thickness will give the onions a nice texture after cooking.

Soak the Onions

Step 2) - Next, place the onion slices in a bowl filled with cold water. Let them soak for a few minutes. This step is optional, but it helps to make the onions more digestible and gives them a milder flavor. If you prefer a stronger onion taste, you can skip this step.

Sauté the Onions

Step 3) - Pour about 4 tablespoons of extra virgin olive oil into a large frying pan. Heat the oil over medium-high heat until it’s hot, but not smoking. Once the oil is ready, add the onion slices to the pan.

Sauté the onions over high heat, stirring occasionally to ensure they cook evenly. At this stage, avoid adding salt; you’ll add it later. The high heat will help caramelize the onions slightly, giving them a rich flavor. After about 3-4 minutes, add a pinch of fine salt to the onions and continue cooking.

Add the Sweet and Sour Flavor

Step 4) - Now it’s time to add the sweet and sour elements to the dish. Sprinkle the sugar over the onions and stir well to coat them evenly. Let the onions cook for about 2 more minutes, allowing the sugar to start dissolving. Then, pour in the vinegar, and stir again to combine everything. Continue to cook the onions, stirring frequently, until the sugar is completely dissolved and the vinegar has evaporated. This process should take about 5 minutes. You’ll know the onions are ready when they’re tender and coated in a glossy, sweet, and tangy sauce.

Taste and Adjust

Step 5) - At this point, taste the onions to check the balance of sweet and sour flavors. Depending on the sweetness of your onions and the acidity of your vinegar, you may want to adjust the amount of sugar to suit your personal taste. If you find the onions are too sour, add a little more sugar, and if they’re too sweet, you can add a splash more vinegar. Buon appetito!

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Storage

You can keep sweet and sour red onions in the refrigerator for up to 3 days by storing them in an airtight container.
When you're ready to eat them, you can serve them at room temperature—just remember to take them out of the fridge about an hour before serving.
If you prefer, you can also reheat them in a pan with a little oil or a splash of water to keep them from sticking or burning.
Freezing these onions is not recommended.

Tips and Variations

Milder Flavor with Balsamic Vinegar

The recipe I've shared is the simplest version of sweet and sour Tropea red onions, but you can easily adjust it to suit your taste. For a milder, sweeter flavor, you can replace the wine vinegar with balsamic vinegar. The balsamic adds a richer, more complex sweetness to the dish.

Sweet and Sour Onions with Raisins

For a twist on the classic recipe, try adding raisins to your sweet and sour red onions. Start by soaking the raisins in lukewarm water for at least 20 minutes to soften them. While the raisins are soaking, prepare the onions as usual by washing and slicing them.

Once the onions have cooked down a bit in the pan, add the softened raisins (make sure to squeeze out the excess water) and let them cook together for a few moments. Then, add the sugar and deglaze with vinegar as described in the original recipe.

For an extra depth of flavor, you can soak the raisins in Rum or Sherry instead of water. The alcohol will evaporate during cooking, leaving behind a wonderfully aromatic dish.

Herbs and Spices for Extra Flavor

Another way to change up the recipe is by incorporating herbs or spices. A great option is to add a few fresh thyme leaves just as the onions are finishing cooking. The thyme will bring a subtle earthiness that pairs beautifully with the sweet and sour onions.

Alternatively, you can add some juniper berries and a few bay leaves while the onions are browning. After adding the sugar and vinegar, remove the juniper and bay leaves at the end of cooking to prevent their flavors from becoming too strong.

Using Butter for a Milder Flavor

If you prefer a milder, creamier taste, you can substitute butter for the olive oil in the recipe. Butter adds a rich, smooth flavor that complements the sweetness of the onions without overpowering them.

This variation works particularly well if you’re serving the onions as a side dish with delicate flavors.

How to Serve

Sweet and sour red onions are a versatile and easy side dish that pairs well with many dishes. They are perfect with braised or grilled red meat, game, or pork, and they also complement flavorful cheeses like pecorino or gorgonzola.

These onions are great for enhancing bread croutons as an appetizer, or for adding to sandwiches with cured meats. They also make an excellent topping for gourmet pizzas.

Quick to prepare, homemade sweet and sour red onions will elevate any dish and are sure to be a hit at the table!

Curiosities

Red Onion from Tropea

The ideal onion for this recipe is the Tropea Red Onion, from the beautiful seaside town of Tropea in Calabria. These are the ones I used for this Italian recipe. This onion is a staple of Calabrian cuisine, known for its exceptional sweetness, whether eaten raw or cooked. Only onions grown along the Calabrian Tyrrhenian coast, from Amantea to Capo Vaticano, can be called Tropea onions.

Though the exact origins of the Tropea onion are unclear, it likely arrived in Italy with the Phoenicians and Greeks over 3,000 years ago. By medieval times, Tropea had become famous for its red onions, mentioned in numerous historical accounts.

The unique sweetness of the Tropea onion comes not from higher sugar content, but from a lower level of Pyruvic acid, making it less pungent and allowing its natural sweetness to shine. Locals say a true Tropea Red Onion is so sweet, you can eat it like an apple!

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STEP BY STEP PHOTOS ABOVE!Have a look at my step-by-step photo instructions, variations and tips. That way, you can get it perfect the first time you try it!