Line a baking tray with baking paper.

Prepare the dough following the instructions here.

Instead of dividing it into balls, transfer it to the tray and gently press it into a large rectangle.

Cover with a tea towel and leave to rest for 1 hour.

While the dough is resting, heat the olive oil in a large heavy-based saucepan over medium heat.

Cook the onion for a few minutes, then reduce the heat to low and cook for about 30 minutes or until the onion is completely collapsed and caramelised.

Preheat the oven to 220°C (425°F).

Gently dimple the top of the focaccia with your fingers, sprinkle with a little sea salt and drizzle with a little olive oil.

Spread about a cup of the caramelised onion over the focaccia dough.

Bake for 20 minutes or until the focaccia is golden brown.