Just before baking, gently dimple the dough again with your fingertips and sprinkle another ½ teaspoon coarse salt all over. Bake the focaccia for about 20 minutes, rotate the pan back to front for even cooking and bake another 10 to 15 minutes, or even longer, until the bread is golden brown and the onions and tomatoes are nicely caramelized.
Scatter the vegetables all over the focaccia and lightly press in with your fingertips, creating dimples in the soft dough. Finally, drizzle the marinating oil over the top. Let the focaccia rise, uncovered, for about 20 minutes. Meanwhile, arrange a rack in the center of the oven (with the baking stone on it, if you have one) and heat to 425°.
With this dough as a base, however, you can be creative and make a focaccia with mushrooms, leeks, sausages or cheese. Keep in mind though that a simple topping, with a few distinct and harmonious flavors, is always more successful than a topping that tries to incorporate too many things.
La Cucina di Lidia (Softcover) buy now. In a medium-size bowl, mix the yeast, warm water, and sugar, and allow it to stand 10 minutes, until foamy. In a large bowl, mix 5 cups of the flour and 1 ½ teaspoons of the salt, forming a well in the center.