In a large bowl place your chopped red onion and balsamic vinegar with a pinch of salt and leave it to sit for 5- 10 minutes.
Then add the tomatoes, olive oil, sourdough and peppers and toss it all together, leaving it to sit for 15 minutes to let the juices infuse.
In the meantime, over a medium to high heat fry off your halloumi in a frying pan with olive oil until it is crisp and golden on the outside.
Season and taste your salad mix and the tip it out onto a large plate/ platter, topping with your halloumi slices, basil leaves and a scattering of chopped olives and let everyone dig in!