Walnut Lattice Cake with Jam

Combine 130g of flour, 250g of sugar, and 100g of ground walnuts in a large mixing bowl. Stir continuously with a wooden spoon and gradually add 125g of melted butter to the mixture. Whip 5 egg whites to stiff peaks, then fold most of them into the batter, reserving some for the topping. Transfer the batter to a greased cake pan. Bake the cake in a preheated oven for 30 minutes. When the cake is done, spread jam of your choice on top, then use a pastry bag to pipe a lattice pattern with the reserved whipped egg whites. Return the cake to the warm oven for a few more minutes.