Red onion, feta & olive tart - Good Food Middle East

Ingredients

• 2 tbsp olive oil
• 2 large red onions, trimmed at the root and cut into thin wedges
• 2 tbsp light muscovado sugar
• 2 tbsp balsamic vinegar
• 375g sheet ready-rolled puff pastry
• 100g feta cheese, crumbled
• 175g black olives, pitted and chopped
• 1 tbsp extra-virgin olive oil