In a large bowl, combine flour, salt, eggs and water. Stir until dough has pulled together, turn it out onto a lightly floured surface then knead until smooth and elastic. If it sticks, add a little oil to your hands. Cover with cling wrap then set aside in refrigerator for about 30 minutes.
Preheat oven to 180 degrees C.
Place bacon in a frying pan over medium heat. Cook until bacon starts to brown. Stir in onion then cook for about 5 minutes. Stir in sauerkraut, apple, water, stock cube, salt and pepper. Reduce heat, cover then simmer for 15 to 20 minutes. Remove from heat and let cool.
Divide the dough into 2 portions. Lightly oil your work surface and roll out the dough into thin sheets about 20x40cm. Pour liquid from sauerkraut into a oblong baking dish then spread bits of butter into it. Spread sauerkraut mixture evenly over the sheets of dough. Roll sheets up widthwise. Cut slices about 5cm wide then place them flat and close together in the baking dish.
Bake in preheated oven for 45 minutes, until dough is lightly browned and liquid has evaporated.