Cut the beef or chicken into fix sized pieces. If you like yo may tie the meat together. Peel the potatoes and cut them length-wise into halves or quarters. Arrange the potatoes and the meat in a pan and place the chopped onion and bay leaves among them. Sprinkle salt, pepper and thyme or cumin on top. Arranfe the sliced tomatoes over the potatoes and the meat and pour the olive oil over them. Dissolve the tomato and pepper paste in enough water to cover most of the potatoes and the meat and put the pan in a well-heated oven. Your dish, which is typically Mediterranean and delicious, will be ready to serve within 1.5-2 hours.