Marmalade cake is cooked in a baking dish with removable bottom. Bottom of the form is covered with parchment paper. Softened butter is mixed with the ground cookies and sugar. Spread the bottom of the form and put in the fridge. Peeled grapefruits are divided into slices, as long as peel and divided into slices, collect their juice. To this juice is added juice of one whole grapefruit. Mix the juice of grapefruit and lemon juice, and put the gelatin and let them rest for 2 minutes. Mix the feta cheese "cream", the sugar, the cottage cheese, egg yolks, grated lemon peel and cream and beat with mixer until a homogeneous mass. Gelatin with the juice is placed on a steam until dissolved. Then allowed to cool for 1-2 minutes, is added to the main mixture and mix again. Egg whites are broken down into the snow and add to mixture. This mixture was poured into the mold. Put it in the refrigerator for one night to set. Once removed, garnish with slices of grapefruit. Finally, after the form is removed, the cake is watered from above with the heated liquid marmalade.