The night before the day when you intend to bake the bread, take your sourdough starter from the fridge and transfer it to a medium-sized bowl. Add 2 cups (500 ml) of warm water, 1 tablespoon of sugar, and mix well. Then, add 3 cups (350-360 g) of rye flour to achieve the thickness of kefyr or sour cream. Cover with a towel or a lid (don't have to seal it, cover it lightly instead), and leave it overnight.
In the morning, stir the starter to achieve a uniform mixture. Transfer 8-10 tablespoon of the starter to a clean jar, put a lid on and keep it in the fridge until the next use.
To the remaining amount of the starter, add 1 tablespoon of sugar, 1 tablespoon of salt, 1 tablespoon of caraway seeds, and approx. 2 cups (240 g) rye flour. Adjust the amount of flour if needed to achieve the desired thickness - when you take a spoonful of the dough, raise it and turn upside down, the dough should be thick enough not to fall off the spoon immediately but it should be moving very slow to fall off the spoon eventually.
Grease the bread pan with soft butter and transfer the dough to the loaf pan.
Level out the surface of the bread with a moist spoon and sprinkle the whole surface of the bread with a seed mix.
Cover the loaf pan with a sheet of parchment paper and transfer to a pre-heated oven at 40 ℃ (104 ℉). Let it rise for approximately an hour.
One an hour has passed, check if the bread has risen 1.5-2 times. If not, let ir rise for another half an hour. If it has increased in volume, increase the temperature in the oven up to 250 ℃ (482 ℉) and bake it for half an hour.
Remove the parchment paper from the loaf pan, decrease the temperature to 195 ℃ (383 ℉) and bake for another 30 minutes.
Remove the bread from the oven. If the bread is well done, it will fall out of the loaf pan easily but you might need to help loosen the bread from the sides of the loaf pan. Transfer it to a baking rack, brush with soft butter, cover with a clean cotton or linen towel and leave it to cool down completely.
Serve it with garlic butter for a rich and salty taste.