Warm quinoa salad with grilled halloumi

INGREDIENTS

• 3 tbsp extra-virgin olive oil
• 1 small red onion , sliced
• 1 large roasted pepper from a jar, thickly sliced, or a handful of ready-roasted sliced peppers
• 200g quinoa
• 500ml vegetable stock
• small bunch flat-leaf parsley , roughly chopped
• zest and juice 1 lemon
• large pinch sugar
• 250g pack halloumi cheese , cut into 6 sliced