This is one of those rather strange, but surprisingly tasty old recipes. The cake itself is not dry at all and has just the right amount of sweetness. Originally taken from a Dalmatian cookbook that has a cult following in Croatia (and is given to pretty much every newlywed couple), and adapted slightly to my own personal preference. You can use any kind of a starchy potato and whatever jam you're currently obsessing over. Here, I have used a homemade apricot jam, though plum or grape jam pairs rather well with the dough, too. —empirical_kitchen
Preheat the oven to 180 degrees C. Cook the potatoes with their skin on until a fork can easily pierce the potatoes. Drain them and leave to cool down. Peel the skin and pass the potatoes through a potato ricer or grate them on the small holes of a box grater.
In a separate bowl, mix 250 g of flour with powdered sugar, baking powder, spices, salt, and the lemon zest. Add the flour mixture to the potatoes, and then add the lemon juice, lard, and the egg.
Stir the mixture with a wooden spoon until everything comes together and you can continue kneading the dough with your hands. You should end up with a slightly sticky dough. If your dough is too sticky, add more flour until you can easily handle it (add 25 g of flour at the time).
Divide the dough into two equal parts. Grease and flour the bottom of a 9" round cake pan and press one half of the dough into the pan. Spread the jam over the dough in a thick layer. Roll out the remaining half of the dough and make a lattice over the jam. Use any remaining dough to form a log and line the cake.
Bake the cake for 45 min or until the top starts to brown. Let the cake cool for 10 min, release it from the pan and leave on a cooling rack until it completely cools down. Sprinkle with powdered sugar before serving.