Wash the lemons and squeeze them into a pot so that they fit tightly. Pour water over them and boil for a couple of minutes.

Place a plate over the lemons to keep them submerged in the water and boil for about 20' until they start to get tender.

Pierce each lemon with a fork in a couple of places so that they get tender faster and continue boiling for an additional 10 minutes until the lemons are very tender.

Using a sifter ladle move them into a deep baking tray and set them aside to cool slightly.

Pour the sugar into the pot where the lemons were boiling and stir over low heat until the sugar dissolves.

Cut the lemons in half, remove the flesh and place it in a cheesecloth, while keeping the peel and pith which you cut into pieces.

Move the pieces of lemon peel as well as the cheesecloth with their flesh into the pot with the sugared water. Turn up the heat and boil the marmalade vigorously for about 15'-20', stirring from time to time. 

When it starts to thicken (the bubbles will become larger) perform the test with the plate. If the marmalade is ready remove the cheesecloth and store in sterilized jars.