Pre-heat the oven to 200°C
Mix salt and flour in a large mixing bowl. Dissolve the yeast in the warm water and leave in a warm place for five minutes until frothy.
Add to the flour and knead the dough in the mixing bowl or on a smooth, clean surface, pushing to stretch the dough with the heel of your hand, then folding the sides together, turning and repeating for about ten minutes until the dough is smooth and glossy. Form into a ball, cover with a tea towel and leave to prove for two hours.
In a large lidded pan, heat the oil on a moderate heat and saute the onions until soft, add the thyme.
Grease a circular quiche dish then knock back the dough into a ball. Roll and stretch the dough to the same size as the quiche dish. Transfer the dough to line the dish and press into the sides with your fingers.
Split the anchovies lengthways, and arrange them acorss the onion base. Dot with the black olives. Leave to rest for a few minutes to allow the dough to rise slightly.
Cook in the oven for 35 minutes. Serve in slices with a seasonal salad.