Red Onion Relish

Red Onion Relish

This easy and delicious recipe is marmalade inspired, soft, sweet caramelised onion relish. Use this recipe to add to so many dishes like hot dogs, homemade burger, roast beef, on breakfast eggs or with cheese. My favourites to use with this relish are a mature cheddar and red onion toastie or with a goats cheese and red onion relish tart.

To see more recipes on ways to preserving onions check out our website. From freezing to pickling we have you covered.

You can adjust the recipe to make it healthier. Instead of olive oil you can use a coconut oil and instead of brown sugar try honey or maple syrup for vegan option. Furthermore, using butter instead of olive oil is also a delicious (not so healthy) alternative. Make this recipe without vinegar if you like. The sugar alone gives a caramelized flavour to the onions – perfect for burger toppings. Although, if you don’t use vinegar it won’t last so should be eaten immediately (or a day or two!)

This recipe uses red wine vinegar and brown sugar for the soft, sweet, caramelized onion flavours. Will keep for 2 months in the fridge.

I love to add in some chopped Rosemary to this, it complements the relish with a deep herb flavour which works great if you are serving with a joint of meat.

red onion relish

Red Onion Relish

Simple Red Onion Relish recipe in 25 minutes
Keyword burgers, marmalade, red onion, relish
Prep Time 5 minutes
Cook Time 20 minutes
Servings 10 tbsp
Calories 21kcal


  • 3 Red Onions
  • 1 tsp Olive Oil
  • 1/2 tsp Salt
  • 1 tbsp Brown Sugar
  • 2 tbsp Red Wine Vinegar
  • 1 sprig Rosemary (chopped) optional


  • Slice the onions and add to pan with the oil and salt, begin to cook over medium heat for 5 minutes to soften. 
  • Stir in the red wine vinegar, the sugar and the rosemary allow to simmer for 2 minutes then reduce heat and cook for further 15 minutes stirring regularly to prevent sticking.  
  • The liquid should all be absorbed and the onions darkened and thicken.  Remove from heat.
  • You can serve warm or decant into a jar and store in the refrigerator up to 2 months. 


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