Pissaladiere

From this cookbook. A beautiful onion and anchovy tart studded with olives. A taste of the rural south of France, and one of my family's favourites!

To make the yeast dough:
250g (2 cups) ‘00’ (Italian) or plain all-purpose flour
3 tsp fresh yeast, or 4 tsp dried
125ml warm water
3 tablespoons olive oil
Pinch salt

Put the flour into an electric mixer with a dough hook, or into a food processor. Alternatively, into a large bowl to mix by hand.
Dissolve the yeast in the warm water: mix well and pour into the flour mixture.
If using an electric mixer, add the oil and salt and beat until the dough is well-blended and leaves the sides of the bowl. Remove, knead into a ball on a floured surface, then transfer to an oiled bowl and leave to prove for one hour.
If using a processor, mix the yeast and flour for ten seconds, then add the salt and pour the oil down the funnel. Process until the dough forms a ball. (You may need a little water). Transfer to an oiled bowl and leave to prove for one hour.
If mixing by hand, use a bread knife to mix the yeast gradually into the flour. Then use your hands to mix until the dough is well-blended and leaves the sides of the bowl. Add more flour or water to achieve a soft, kneadable dough. Knead on a floured surface for a few minutes or until soft and supple, then transfer to an oiled bowl and leave to prove for one hour.

To make the filling:
100ml olive oil
approx. 1.25 kg brown onions, peeled and thinly sliced
3 sprigs of fresh thyme leaves (or half tsp dried)
salt
pepper
One tin anchovy fillets, sliced in half lengthways
About 20 small black olives

Heat the olive oil in a big heavy saucepan. Sauté the onions briefly, tossing with a wooden spatula. When the onions are well greased but not brown, add the thyme leaves. Reduce the heat to low and cook slowly, stirring occasionally, for about 45 minutes, or until they have a brown sheen and are completely softened.
(Failure to do this results in a strong, indigestible onion flavour). Don’t let the onions burn though.

When the dough has risen, roll it into a large circle or rectangle to fit a large baking tray. Place the dough on the lightly-greased tray, and spread the onions on top, leaving a small border. Arrange the anchovies in a spoke or grid pattern and dot with olives. Season lightly if you must. Wait 15 minutes to let the dough rise around the filling. Bake in a preheated 220C oven for around 30 to 35 minutes.
Best when warm or at room temperature.