1. Chop the onions and place them in a small pot with water in order for them to soften.
2. Grate the tomatoes and add them to the pot, along with the bay leaf, the oregano, as well as, salt and pepper. Cover the pot and leave on heat until almost of the liquid has been absorbed. Then add the olive oil, and reduce heat by half until the mixture thickens.
3. Grease a pan with olive oil and lay two layers of phyllo that has already been greased with olive oil. Pour half of the tomato & onion mixture into the pan and cover with another layer of phyllo. Then pour the rest of the filling, cover it with two more layers and crimp the edges well.
4. After spreading some more olive oil on the surface of the top phyllo, sprinkle with lukewarm water and bake the pie at 180°C for 40 minutes.