Sourdough Onion Focaccia (Printable)

Chewy sourdough bread with caramelized onions and sea salt, offering an airy texture and savory topping.

# What You'll 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 tablespoon olive oil
08 - 1 teaspoon flaky sea salt
09 - 1 teaspoon fresh rosemary leaves, optional
10 - Freshly ground black pepper to taste, optional

# How to Make It:

01 - In a large bowl, combine sourdough starter, bread flour, and lukewarm water until a shaggy dough forms. Cover and let rest for 30 minutes to allow the flour to fully hydrate.
02 - Add fine sea salt and olive oil to the dough. Mix thoroughly until both ingredients are evenly distributed throughout.
03 - Over the next 2 hours, perform 3 to 4 sets of stretch and folds at 30-minute intervals. Wet your hand, grab one side of the dough, stretch it up and fold it over itself. Rotate the bowl and repeat on all four sides.
04 - Cover the bowl and allow the dough to rise at room temperature for 6 to 8 hours until it has doubled in size.
05 - Generously oil a 9x13-inch baking pan. Gently transfer the dough to the pan without deflating it. Using oiled fingertips, stretch and press the dough to fit the entire pan surface.
06 - Cover the pan with plastic wrap and refrigerate for 8 to 12 hours. This extended cold fermentation develops maximum flavor and improves texture.
07 - While dough chills, heat 1 tablespoon olive oil in a skillet over medium-low heat. Add sliced onions and cook, stirring occasionally, for 20 to 25 minutes until golden, tender, and sweet. Transfer to a plate and cool completely.
08 - Remove dough from refrigerator and let rest at room temperature for approximately 1 hour before baking.
09 - Preheat oven to 425°F (220°C). Using your fingertips, dimple the entire surface of the dough. Drizzle with additional olive oil. Evenly distribute caramelized onions, flaky sea salt, fresh rosemary, and black pepper across the top.
10 - Bake for 25 to 30 minutes until the surface is golden brown and the edges are crisp. The focaccia should sound hollow when tapped on the bottom.
11 - Remove from oven and cool for a few minutes before slicing and serving. Serve warm for optimal texture and flavor.

# Expert Advice:

01 -
  • The overnight cold fermentation gives you that deep, complex sourdough flavor that tastes like you've been baking for years.
  • Caramelized onions make it feel fancy enough to serve at a dinner party but the method is so forgiving you'll make it constantly.
  • One dough, zero commercial yeast, and you get that gorgeous open crumb with crispy edges that slice beautifully.
02 -
  • Your starter's health and activity level are everything—if it's sluggish the whole timeline changes, so keep it fed and happy and watch for clear signs of peak (lots of bubbles, dome on top, or just past double) before using.
  • The overnight cold ferment isn't optional, it's where the magic happens flavor-wise and texture-wise, so don't skip it or rush it.
  • Caramelizing onions truly takes time and you cannot rush it—medium-low heat for 20–25 minutes is the real method, not high heat for 5 minutes.
03 -
  • Keep your oven temperature accurate with an oven thermometer because even 25 degrees off can mean the difference between golden and pale or burnt edges.
  • Dimpling the dough right before topping prevents it from puffing up and losing those beautiful dimples during baking—press gently but firmly with your fingertips.
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