Oniony Focaccia (Focaccia alla cipolla)

INGREDIENTS:
10 cups (1 k) flour
1 ounce (25 g) active yeast
1/3 cup extravirgin olive oil
One large onion, thinly sliced.
Salt

Dissolve the yeast in warm water.

Put the flour on your work surface, scoop a well in it, and pour in 6 tablespoons of oil, 3 pinches of salt, the yeast, and sufficient warm water to obtain a firm smooth dough.

Knead it for 10 minutes, cover it, and let it rest for 2 hours.
Preheat your oven to 400 F (200 C).

Grease a baking sheet, dust it with salt, then spread the dough over the sheet, tamping it down with a spoon to give it a dimpled appearance, and bake it for 20 minutes.

Three minutes before it's done, sprinkle the finely sliced onion over it. Serve it hot, cut into squares.