1Combine the buttermilk and the warm water in a bowl. Place the flour, salt, sugar and yeast in the bowl of a stand mixer. Using the dough hook, mix on low speed to combine.
2Slowly add the buttermilk mixture and knead on medium speed for 7 minutes or until the dough is smooth and elastic.
3Add the butter and continue kneading until the butter is worked into the dough.
4Transfer the dough to heatproof bowl and cover with plastic wrap. Place the bowl in the oven in rack position 8.
5Select PROOF/ 88°F/CONVECTION/ 40 MINUTES and press START. Proof the dough until doubled in size.
6Grease a 9-inch x 5-inch loaf pan with butter and coat with flour, shaking out the excess flour.
7Turn the dough out onto a lightly floured surface and knead until smooth. Shape the dough into an 8-inch log and place it into the pan. Loosely cover with plastic wrap and place in the oven in rack position 8.
8Select PROOF/ 88°F (31°C)/CONVECTION/ 40 MINUTES and press START. Proof the dough until it rises just above the pan.
9Remove the dough from the oven.
10Reset the oven. Select BAKE/ 350°F/CONVECTION / 40 MINUTES and press START to preheat.
11Carefully remove the plastic wrap. Place the extra flour in a sieve and lightly dust the loaf with flour.
12Once preheated, place the loaf in the oven and bake for 40 minutes until golden brown.
13Cool in the pan for 10 minutes before turning onto a wire rack. Slice and serve warm or at room temperature.