Preheat the oven to 200°C/ Fan 180°C/Gas 6. Cut 3 peppers and 1 red onion into chunks, then place them onto a baking tray. Add half a lemon, face down into the tray. Place the tray into a preheated oven for 45 minutes.
Once the peppers are beginning to char, remove the tray. Add one third of the pepper and onion mixture, and the pulp of the roast lemon to a blender, with a teaspoon each of smoked paprika and oregano.
Add one tablespoon of red wine vinegar, a red chilli and a garlic clove. Season with salt and pepper and add a tablespoon of rapeseed oil. Blitz in a food processor until smooth.
Slice your halloumi then place it on a hot griddle pan. Cook the halloumi slices on a medium high heat for 2–3 minutes on each side, until golden brown.
Toast 4 brioche burger buns and mix your blitzed peri peri sauce with 5 tbsps of mayonnaise.
Take a bun. Add a layer of peri peri mayo. Then a slice of halloumi, followed by some of the roasted peppers, some lettuce leaves, more mayo, more halloumi and then top it with the bun lid. And voila! A finger-licking stacked veggie burger!