Add 1 cup warm water (about 105–115°F / 40–46°C) and 2 tbsp olive oil to the well. Stir with a wooden spoon or dough scraper until combined and no dry flour remains.

Turn the dough out onto a lightly floured surface and knead for 6–8 minutes until smooth and elastic. If dough is very sticky, dust with up to 2 tbsp more flour.

Form into a ball, lightly oil the inside of the mixing bowl with a little olive oil, place the dough inside, cover with plastic wrap or a clean towel, and let rise in a warm draft-free place for 1 to 1.25 hours, until roughly doubled in size.

After rising, gently deflate the dough and transfer it to a baking sheet (13x9-inch) or a large round tart pan (11–12-inch). Stretch or roll the dough to fit the pan, leaving a slightly thicker edge. If using a rimmed baking sheet, create a 1/2-inch border by pushing dough inward slightly.

Onion Filling

Slice and caramelize onions

While the dough rises, prepare the onions. Heat 2 tbsp unsalted butter and 2 tbsp olive oil in a large wide skillet or sauté pan over medium-low heat. Add 1.5 lbs thinly sliced yellow onions and stir to coat.

Season with 0.5 tsp granulated sugar and 1 tsp fine sea salt. Cook the onions slowly, stirring every 3–5 minutes, keeping the heat low enough that the onions sweat and soften without browning too quickly. This should take 25–35 minutes until the onions are deeply soft and lightly golden.

When onions are soft and beginning to color, increase heat to medium and add 1/4 cup dry white wine or dry vermouth to deglaze the pan. Scrape up any browned bits and continue cooking until most of the liquid has evaporated, about 3–4 minutes. Adjust seasoning with 1/2 tsp freshly ground black pepper and more salt if needed. Remove from heat and let cool slightly.

Assemble & Top

Preheat and prepare base

Preheat oven to 425°F (220°C). If you like a crisper bottom, place a baking stone or an inverted heavy baking sheet in the oven while it preheats. If using an egg wash, beat 1 egg with 1 tsp water and brush the dough border lightly.

Spread the cooled caramelized onions evenly over the stretched dough, leaving a 1/2-inch rim.

Arrange 10 drained anchovy fillets in a decorative pattern on top of the onions (traditional is radiating lines or crisscross). Place 12 pitted Niçoise or Kalamata olives whole or halved between anchovy strips. Scatter 1 tsp fresh thyme leaves over the tart.

Drizzle 2 tbsp extra-virgin olive oil lightly over the assembled tart and sprinkle 1/4 tsp coarse sea salt. Optionally grate 1/2 tsp lemon zest over the top for brightness.

Bake & Serve

Slide the tart into the preheated oven onto the hot stone or baking sheet. Bake at 425°F (220°C) for 15–22 minutes, until the crust is golden and crisp and the edges are puffed and set. If the onions begin to brown too fast, tent with foil for the last 5 minutes.

Remove from the oven and let the pissaladière rest on a rack for 5–10 minutes. Drizzle an extra small splash (about 1 tsp) of olive oil if desired.

Slice into wedges and serve warm or at room temperature. Pissaladière is often served as an appetizer or light main with a simple green salad.