Prepare the sourdough starter if you don't have yet. Mix the rye flour and water. Let it stand minimum 12 hours, the longer and more feedings will be better. Please refer to my sourdough starter recipe

After 12 hours. Mix the 400 gr sourdough starter, flour and water. Mix it until incorporated.

Let it autolyse or rest for 30 minutes

Add the salt and fold the bread 4 times so the salt get into the dough. You may sprinkle water too.

Knead the dough for 8 - 10 minutes until it is smooth. (optional method: stretch and fold the dough method for 2 hours- every half and hour stretch the dough and bring back the dough into the middle and let it rest)

Prepare the bannetone or bowl lined with kitchen towel and dust the bowl generously. So the dough will not stick on the bannetone.

Shape the dough into the ball shape, dust some flour on the top of dough and place it upside down into the bannentone.

Cover the bannetone with plastic bag or plastic wrap or shower cap if any.

Let it proof/ rest for minimum 4 hours in room temperature or 2 hours in fridge and 2 hours in room temperature or overnight in the fridge

Check the dough by poke it. If the poke stay longer in the dough /not so quick spring back, it means the dough is ready to be baked.

Pre-heat your oven to 235 C and prepare a pan of hot water and place it at the bottom of oven to create steam.

Take out the hot baking tray. Place your dough on top of the baking tray. Be careful, it is very hot. Score the dough with sharp thin knife or razor blade.

After 35 minutes baking, check the bread. If you like a bit darker crust, bake it again.

Remove it out and let it rest for 15 minutes and listen to the crust sound of the bread and smells good. After 15 minutes, you may slice the bread.