The recipe



Peel a large onion, roughly chop, then let it cook over a moderate heat in a large pan with 3 tbsp of olive oil. Roughly chop 400g of carrots then, when the onion is soft and translucent, add it to the pan and leave it to cook with the occasional stir, for 10 minutes.

Pour in 1.2 litres of water, bring to the boil, then lower the heat to a gentle simmer. Season with salt and black pepper, then leave it to cook for about 30 minutes on a low to moderate heat, again with the occasional stir.

Chop 500g of ripe tomatoes and put them in a shallow pan over a medium heat with 3 tbsp of olive oil and let them cook down to a slushy consistency.

Add 10 large basil leaves, stir the tomatoes into the carrots, then reduce the vegetable mixture to a rough purée using a stick blender. Pour it into shallow bowls. Roughly crumble 200g of feta cheese and scatter it over the soup. Enough for 3 or 4.

The trick



Keep the cooking brief. The fresh flavours of the summer carrots and tomatoes will disappear if you simmer the soup for too long. Add the basil at the last minute in order to keep its peppery notes vibrant.

The twist



Use vegetable stock instead of water, but choose a light version rather than anything too strongly flavoured that will overpower the tomatoes and summer carrots. This also makes a bright and fresh-tasting chilled soup. Make it early in the day, then chill the soup thoroughly, stirring in ice cubes at the table.

Email Nigel at nigel.slater@observer.co.uk or follow him on Twitter@NigelSlater