Sourdough Onion Focaccia (Printable Version)

Airy sourdough focaccia topped with sweet caramelized onions and a hint of sea salt.

# What You Need:

→ Sourdough Starter

01 - 3.5 oz active sourdough starter at 100% hydration

→ Dough

02 - 14.1 oz bread flour
03 - 10.1 fl oz lukewarm water
04 - 0.35 oz fine sea salt
05 - 0.68 fl oz extra-virgin olive oil

→ Topping

06 - 2 medium yellow onions, thinly sliced
07 - 1 tbsp olive oil
08 - 1 tsp flaky sea salt
09 - 1 tsp fresh rosemary leaves
10 - Freshly ground black pepper to taste

# How To Make:

01 - In a large bowl, mix the sourdough starter, bread flour, and lukewarm water until a shaggy dough forms. Cover and let rest for 30 minutes.
02 - Add fine sea salt and olive oil to the dough. Mix thoroughly until fully incorporated.
03 - Over the next 2 hours, perform 3 to 4 sets of stretch and folds every 30 minutes to develop gluten strength.
04 - Cover the bowl and allow the dough to rise at room temperature for 6 to 8 hours until doubled in size.
05 - Generously oil a 9x13-inch baking pan. Gently transfer the dough to the pan without deflating it.
06 - Using oiled fingers, gently stretch and press the dough to fit the pan. Cover and refrigerate for 8 to 12 hours.
07 - While dough rests, heat 1 tbsp olive oil in a skillet over medium-low heat. Add sliced onions and cook, stirring occasionally, for 20 to 25 minutes until golden and sweet. Cool completely.
08 - Remove the dough from the refrigerator and let it rest at room temperature for approximately 1 hour.
09 - Preheat oven to 425°F. Dimple the dough with fingertips, drizzle with additional olive oil, then distribute caramelized onions, sea salt, rosemary, and black pepper evenly over the surface.
10 - Bake for 25 to 30 minutes until golden brown with crisp edges.
11 - Allow the focaccia to cool slightly before slicing and serving.

# Cooking Tips:

01 -
  • The sourdough starter gives you that bakery tang and complex flavor without any commercial yeast to worry about.
  • Overnight fermentation means you do the real work when it suits you, then wake up to something that smells incredible.
  • Those caramelized onions are the difference between bread and an experience—soft, sweet, and utterly irresistible.
  • It looks impressive enough to bring to gatherings but forgiving enough that minor imperfections somehow add to the rustic charm.
02 -
  • The overnight cold fermentation isn't optional laziness—it's where the real flavor develops and the dough becomes forgiving enough to dimple without tearing, so don't skip it thinking a faster timeline will work.
  • Caramelizing onions low and slow for 20 to 25 minutes transforms them from sharp to sweet and jammy; if you rush this step on high heat, you'll end up with onions that taste burnt rather than honeyed, and the whole dish loses its soul.
03 -
  • If your kitchen is cold, place the dough in a proofing box, warming drawer, or even an oven with just the light on; sourdough fermentation slows dramatically below 18°C, and patience only works if warmth is part of the equation.
  • Save a little of your caramelized onions and drizzle them with aged balsamic vinegar for a side condiment—guests will ask what the secret ingredient is, and you'll smile knowing it's just time and attention.
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