We start preparing the crust: Put into a bowl the margarine and flour and knead to combine. When it forms into crumbs, add the egg yolks, sugar, salt, water and knead to combine, until a smooth dough forms. We wrap it in plastic wrap and place it in the fridge for 30 minutes. This way the dough will chill and it will be easier to handle.
Now we will prepare the lemon custard cream in “bain marrie”: In order to do so, place flour, sugar, egg yolks and water into a large metal bowl, set on top of a saucepan, with simmering water. Make sure that the bowl is not submerged in the water. Stir mixture with a wooden spoon, until it thickens. Then we add the lemon juice, margarine and continue stirring, till combined. Carefully remove the bowl.
Preheat the oven at 350o F.
We remove the dough from the fridge, unwrap it and place it between two plastic wrap sheets, so dough will not stick, while rolling it out. Using a rolling pin, roll it out on your work surface, into a thin sheet.
Lay the dough sheet in a tart pan, making sure that the bottom, as well as the inside of the pan are covered. Use a fork to prick the dough and then bake in the preheated oven for about 15-20 minutes, until slightly browned.
Remove the pan and allow to cool for 10 minutes and then spread evenly on top the lemon custard. Place the pan back into the oven and continue baking for an additional 15-20 more minutes.
We remove the pan from the oven and allow cooling. Then put the “lemonopita” in the fridge for at least 1-2 hours, prior to serving.