Baked sea bass with romesco sauce

INGREDIENTS

• 4 red peppers , deseeded and cut into large chunks
• 2 yellow peppers , deseeded and cut into large chunks
• 2 large tomatoes , halved (choose on the vine for best flavour)
• 1 large red onion , cut into wedges
• 4 large garlic cloves
• 4 tbsp olive oil , plus extra for drizzling
• 2 x 1kg/2lb 4oz whole line-caught sea bass , scaled and gutted
• 2 lemons , thinly sliced
• 2 large handfuls fresh mixed herbs (such as rosemary and thyme)
• 2 tsp balsamic vinegar
• 50g whole hazelnuts , toasted