II
The Method
1
Combine the flour, yeast, and salt in a large bowl. Add the cold water and olive oil. Mix to a shaggy dough, then knead by hand or on a medium-speed machine for 8–10 minutes until the dough is smooth, supple, and pulls cleanly from the bowl. The hydration is 65–70 percent; the dough will feel softer and stickier than a lean bread dough — this is correct. Cover tightly and refrigerate for 12–24 hours. The dough is ready when it has at least doubled in volume and the surface shows a network of bubbles.
2
Warm the olive oil in a wide, heavy pan over low heat. Add the thinly sliced onions and a pinch of salt. Cook, stirring occasionally, for 30 minutes. This step is where the dish lives or dies: the onions must collapse entirely into a pale-gold, jammy mass with no residual sharpness — if they retain texture or any raw bite, the sauce will never achieve the characteristic sweetness that anchors the sfincione. Add the mashed tomatoes, raise the heat briefly to combine, then reduce to a simmer and cook a further 10 minutes until the sauce is thick and cohesive. Taste: it should be sweet, with no acidity remaining.
3
Remove the dough from the refrigerator and allow it to stand at room temperature for 1 hour. Generously oil a 30 × 40 cm rimmed baking tray. Transfer the dough to the tray and, using oiled hands, press it gently outward to fill the tray. Do not force it; if it springs back, rest it for 10 minutes and continue. The dough is ready for topping when it holds its pressed shape without retracting and the surface feels airy and pillowy to the touch.
4
Arrange the sliced tuma evenly over the dough surface. Lay the desalted anchovy fillets over the cheese. Spread the onion-tomato sauce over everything in an even layer, covering the cheese and anchovies completely. The anchovies will melt and infuse the sauce during baking.
5
Toss the breadcrumbs thoroughly with the 45 ml of olive oil until every crumb glistens — dry crumbs will scorch before the dough is cooked through. Scatter the oiled crumbs evenly over the sauce. Sprinkle with dried oregano. The assembled sfincione should show an even, pale-gold crumb layer with no dry patches.
6
Bake at 220 °C (conventional oven, lower-middle shelf) for 25–30 minutes. The sfincione is done when the breadcrumb crust is deep golden and crackling-firm to a light tap, the edges of the dough have pulled slightly from the tray sides and are well coloured, and the kitchen carries a strong smell of toasted bread and caramelised onion.
7
Remove from the oven and drizzle immediately with a thread of extra-virgin olive oil — this is the traditional sfincionari finish. Allow to rest in the tray for 2–3 hours before cutting. Served hot, the oil burns the palate; served cold, it congeals. At room temperature the crumb relaxes, the flavours consolidate, and the crust retains its contrast.