Peel and thinly slice the onions. Heat the oil in a wide saucepan. Steam onions in it at low heat for about 20 minutes without letting colour take. Add bay leaf and season with salt, pepper and sugar
Wash the thyme, shake dry and chop the leaves coarsely. Drain the olives and sardines. Divide sardines into 2 fillets each
Unroll the dough and place it on a baking tray with the baking paper. Add thyme to the onions and season again. Remove bay leaf. Cover dough with onions, sardine fillets and olives
Bake the pizza in a preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: see manufacturer) for 15-20 minutes. Serve hot, lukewarm or cold