Preheat the oven to 180c. Grease the muffin cups with oil. Lightly pan-fried the bacon, leave aside. Place 3 sheets of pastry into the muffin tin, brush with oil. Repeat the process two more times until the tin is well covered. Line the pastry cases with few spinach leaves, place the tomato cut side up, add some bacon pieces and chopped onions. Carefully break an egg into the case. If you are using a muffin tray, fill the unused hole with water. Bake for 20 minutes or until the egg white has set. Use a knife to lift up the tart and stand for 5 minutes before serving.