In a saucepan over a medium to low heat, gently simmer the red wine vinegar, whole peppercorns, red chilli, deseeded and sliced, and caster sugar for 5 minutes.

Remove from the heat and pour the liquid over the peeled and thinly sliced red onions. Chill overnight.

To serve, cut a loaf of fresh rye bread into 8 slices and spread each slice with hummus and a drizzle of extra-virgin olive oil. Top with the pickled onions and sprinkle with lemony sumac or a good crack of freshly ground black pepper.