Preheat the oven to 375 degrees F. Line a large baking sheet with parchment paper and set aside.
In a large bowl, sieve together the flour, baking powder, cardamom, nutmeg and salt. Pour onto a pastry board or clean countertop. Make a large well in the middle. Add the sugar, vanilla extract, rum, lemon juice and zest, and the eggs into the well. Mix the ingredients in the middle together to break up the eggs first and then draw flour in from the sides and mix/knead together until you have a stiff dough.
Mix together the currants, golden raisins, chopped almonds and candied lemon peel together in a medium bowl. Set aside. Flatten out the stiff dough. Cut the cold butter into small pieces and add it on top of the dough evenly. Pour the fruit and nut mixture on top and then the quark or cottage cheese. Mix and fold the dough over with your hands until everything is evenly incorporated. It gets messy but it's fun!
Use a knife to cut the dough into two equal amounts. Shape each into a long oval and fold it over once lengthwise to give it that traditional stollen shape. Use floured hands as necessary. Place each stollen diagonally on the baking sheet with lots of space between them.
Bake for 50 minutes or until dark brown on top and a toothpick poked in the centre comes out clean. If you have a crazy oven like mine, place another baking sheet underneath on the lower rack to deflect heat and prevent the bottom of the stollen from burning.
While the stollen is still hot from the oven, brush it with the melted butter, additional rum (optional), and dust thickly with icing sugar. Let cool. Before slicing and serving, dust with additional icing sugar.