Butter the loaf pan. Remove the dough from the fridge and use a sharp knife to cut it decisively in half lengthwise. Twist the two halves of the dough around each other, tuck the ends underneath themselves, and lay the babka into the prepared pan.

Let it proof in a warm (75°–86°F / 24°–30°C) place for about 2 hours, until the babka has doubled in size and looks swollen.