Sweet onions caramelized atop golden focaccia create an irresistible savory-sweet bread. This vegetarian mediterranean flatbread is a family crowd-pleaser at any meal.
Combine the all-purpose flour, sugar, and active dry yeast in a large mixing bowl. Pour in warm water and mix until a sticky dough forms. Let rest 5 minutes.
Add 2 tbsp olive oil and 1.5 tsp kosher salt. Knead the dough on a lightly floured surface for 8–10 minutes until smooth. Place dough in an oiled bowl, cover, and allow to rise in a warm spot for about 60–75 minutes, until doubled in size.
Meanwhile, slice onions thinly. In a large skillet, heat 2 tbsp olive oil over medium-low heat. Add the onions and 0.5 tsp salt. Slowly caramelize for 18–22 minutes, stirring occasionally, until deeply golden but not burnt. Set aside.
Oil a 9x13-inch baking pan with 1 tbsp olive oil. Stretch the risen dough gently into the pan, pressing all the way to the edges. Use your fingers to dimple the surface deeply. Cover and let rise for another 30 minutes.
Preheat oven to 425°F (220°C). Evenly scatter the caramelized onions over the dough. Drizzle with the remaining olive oil, sprinkle with fresh rosemary and black pepper. Bake for 21–24 minutes, until the focaccia is deeply browned and crisp on the edges. Let cool slightly before slicing and serving.