Peel the red onions and remove the root and stem ends. Cut each onion in half and chop it into small, even pieces. You can also slice the onions thinly if you prefer a more traditional onion salad texture. Transfer the prepared onions to a large mixing bowl, separating any pieces that have stuck together. If the onions taste particularly strong, rinse them briefly under cold water and drain thoroughly.

In a separate small bowl, combine the tomato ketchup, mint sauce, lemon juice, paprika, ground cumin, ground coriander, chilli powder, and salt. Stir everything together until you have a smooth, evenly coloured dressing. If you enjoy a slightly sweeter flavour, add a teaspoon of mango chutney or a small pinch of sugar. Taste the dressing and adjust the chilli or lemon juice according to your preference.

Pour the prepared dressing over the chopped onions. Using a spoon, mix everything thoroughly until the onion pieces are evenly coated. Make sure the dressing reaches the bottom of the bowl so all the ingredients are combined properly. Add the finely chopped fresh coriander and mix again. The onions should look glossy and colourful, with the red onion pieces coated in the tangy, reddish dressing.

Taste the mixture and adjust the seasoning if necessary. Add extra lemon juice for more tanginess, a little chilli powder for additional heat, or a small amount of mint sauce for a fresher flavour. If the dressing tastes too sharp, add a little ketchup or mango chutney to balance it. Remember that the flavour will develop as the onions rest, so avoid adding too much seasoning immediately.

Cover the mixing bowl with cling film or transfer the mixture into an airtight container. Place it in the refrigerator for approximately 20–30 minutes. This resting time allows the onion pieces to absorb the flavours of the dressing and spices. You can leave them for longer if preparing ahead, although freshly prepared onions will retain the best crunch.

Remove the spiced onions from the refrigerator and give everything a gentle stir before serving. Transfer them to a small serving bowl and garnish with a little freshly chopped coriander. Serve alongside crispy poppadoms, mango chutney, mint yoghurt sauce, or your favourite homemade curry. Enjoy immediately while the onions are fresh and crunchy.