Start by melting the olive oil and cooking the finely chopped onion over a low heat with the basil. Important that it doesn't take any colour. After a couple of minutes I usually add a little water then turn down the heat, cover with a lid and leave to 'sweat' for 5 minutes.
When the onion is translucent add the tinned tomatoes. Please don't skimp when you buy your tinned tomatoes - you get what you pay for - the cherry tomatoes have an even more intense flavour. 3 large tins is exactly the right amount.
At the same time add the red peppers. Drain them first. Simmer, covered for about 10 minutes. You can, if you wish, use fresh peppers but you will need to burn the skins and de-seed (you would need 4 large fresh red peppers - no other colour works). The ready prepared variety are much easier and there is no loss of flavour. I buy mine in a jar - they have been charred and the skin removed and are with brine/vinegar.
Allow the soup to cool a little. Add the sweet chilli sauce - I usually add a good 'glug' - if I had to give a quantity I would say around 4 tbs - but to your taste. Dont miss it out though as it doesn't taste the same without it.
Liquidise the soup, adding the feta cheese which you should cut into small cubes.
Reheat to serve but don't let it boil. The flavour is so intense it is perfect as it is but, for a dinner party, you could crumble some extra feta on the top and add a bit of basil.
A crowd pleaser and always sure to impress.