Preheat the oven to 450F and grease a large pan with olive oil, or line with parchment paper.
Gently deflate the dough and transfer it to the prepared pan.
Use your finger to stretch the dough to fit the pan. If the dough bounces back, let it rest for a few minutes, then try again.
Brush the top of the dough with the egg wash.
Sprinkle with the onion topping and bake over the lowest oven shelf for 15-17 minutes, turning the pan at the 8 minutes mark.
The bread is ready when it is dark golden brown.
Remove from the oven, allow it to cool for five minutes, then slice and serve.