For the paste: Overturn slowly the water on the flour in a big bowl and turn round with a wood spoon. Add 3 spoons of olive oil, salt and the sachet of yeast. Knead in order to obtain a homogenous paste .
For the onions: Cut the onions slicy and cooked them very slowly in a spoon of olive oil. Switch on the oven at 250°C. Drop the paste on a dish, cover the paste with the cooked onions et put the olives and the anchovis on. Spread a little bit a olive oil on top and out in the oven during 20 minutes. Cut the "pissaladiere" in several pieces and serve for the aperitif.