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Rosemary-Balsamic Onions

These rosemary-balsamic onions offer a sophisticated balance of sweetness and acidity, making them a versatile addition to any cook's repertoire. This vegan side dish relies on the slow caramelisation of red onions, which are enhanced by the woody fragrance of fresh rosemary and the deep, rich notes of balsamic vinegar. The addition of a little soy sauce provides an essential savoury depth, resulting in a glossy, jammy finish that elevates the humble onion into something truly special.

Perfect as a topping for plant-based burgers, a garnish for grilled proteins, or even stirred through a warm grain salad, these onions are incredibly simple to prepare. They can be made in advance and kept in the fridge, making them an excellent choice for a stress-free dinner party or a quick weeknight flavour boost. Serve them warm or at room temperature to bring a gourmet touch to your favourite British classics.

Continue reading below

Ingredients for Rosemary-Balsamic Onions

  • 2 tablespoons extra-virgin olive oil

  • 1 large red onion, halved and thinly sliced

  • Salt and pepper

  • 1 rosemary sprig

  • 1 tablespoon balsamic vinegar

  • 2 teaspoons soy sauce

How to make Rosemary-Balsamic Onions

In a large skillet, heat the olive oil. Add the onions, season lightly with salt and pepper and cook over moderate heat until they start to soften, about 5 minutes. Add the rosemary and continue cooking the onions until very soft and just starting to brown, about 10 minutes longer.

Add the balsamic vinegar and soy sauce and cook just until the liquid is mostly evaporated, about 1 minute. Remove the rosemary sprig and serve.

Disclaimer

While every effort has been made to ensure the information is accurate and up to date, individual needs may vary and dietary requirements can differ based on personal health conditions. Always check food labels and allergen information before preparing or consuming any recipe. If you have specific health concerns, allergies, intolerances, or are following a medically prescribed diet, seek advice from your GP, pharmacist, or a registered dietitian before making significant changes to your diet or lifestyle.

Article history

The information on this page is peer reviewed by qualified clinicians.

  • 16 Jan 2026 | Originally published

    Authored by:

    UK recipe editors

    Peer reviewed by

    UK recipe editors
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