If your quark is lumpy or you're using a substitute such as cottage cheese, whisk or beat your cheese till it's smooth before adding it to the batter.
Separate the eggs and add the egg yolks into the large bowl. Put the whites into a one quart or bigger mixing container.
Place the sugar, butter, flour, baking powder, vanilla, lemon juice and zest into the large bowl. Beat till smooth. Add the blended cheese and half the cream, and beat till smooth and incorporated.
Add a pinch of salt to the egg whites, and, using egg beaters or a hand mixer, beat the egg whites till very stiff and you can make a clean cut with a knife.
Beat the rest of the cream until firm and peaks form, avoid over beating.
Fold the egg white and then the cream very gently into the batter to keep it nice and fluffy.
Pour the batter into the prepared crust, smoothe the top and place it into the oven on the lower rack. Bake for about an hour.
Cheesecake is prone to cracking, but if you cut around the edge of the cake, between the batter and the crust about halfway through baking (after 30 minutes), it should help minimize cracking.I didn't do that, but I don't mind cracking, it's just cosmetic, but if you're serving it to guests you might care and can try this trick. Your cake is done when the center is set up and firm when pressed and a toothpick comes out fairly clean. Leave the cake in the oven for another hour with the door cracked slightly open.
Take it out of the oven and cool completely, before taking it out of the form.
Do not refrigerate until it is cooled all the way.
Store in the refrigerator until use. If you cover it with berries, it's best to remove the berries before storing leftovers. It will be good for up to 5 days in the refrigerator. Freeze any leftovers for up to 3 months.