Meanwhile, put together your onions: Heat a big sauté pan about medium heat. The moment hot, insert 2 tablespoons olive oil. After the oil is heated, increase the onions and 1 teaspoon kosher salt. Cook onions, stirring each individual moment or two, till a medium brown, nearly caramel colored, about 25 minutes. [See Note at end.] Scrape onions onto a plate to amazing although you complete the bread.
Finish the focaccia: When the dough is doubled, pour 2 tablespoons olive oil into a 9×13 cake pan. Do not deflate your dough, just scrape it into the oiled pan. Drizzle the top of the dough with another tablespoon of olive oil and use your fingers to dimple the dough, flattening it out. It is okay if it doesn’t arrive at the edges. Enable the dimpled dough relaxation at area temperature for 15 minutes and warmth your oven to 425°F. Following 15 minutes, dimple the dough only where by wanted a little additional into the corners. Permit relaxation for a closing 15 minutes before scattering the top with onions, poppy seeds, and a number of pinches of salt.
Bake the focaccia: For 25 minutes, until finally deeply golden brown at the edges and throughout the top. When it bakes, you can prepare any toppings you’d like to serve it with, this sort of as cream cheese or butter, lox, thinly sliced tomatoes, cucumbers, onions, or capers.
To serve: Loosen the focaccia if it’s stuck in any location and slide it into a cutting board. Slash into 12 squares, using a sharp knife to get by means of the onions on best devoid of pulling them off, and replacing any that scatter. Consume suitable away.
Do ahead: Focaccia retains at space temperature for 1 to 2 days. Reheat on a baking sheet at 350°F for 10 to 12 minutes.
Observe: These are not caramelized onions we do not need 60 to 90 minutes above reduced heat with continual stirring. That is not how any ancestor of mine cooked onions. I’m intentionally employing a bigger heat for much more swiftly developed flavor. If they’re not picking up coloration by 20 minutes, bump up the heat somewhat. If they are coloring too fast to make it to 20 to 25 minutes, cut down the heat. We want to halting shy of a dark bronzed shade, as the onions will finish in the oven and we don’t want them to melt away.