Make sure your sourdough starter is active and bubbly. Feed it 4-6 hours before you begin baking. I use a 50% hydration starter and mix a LEVAIN up the night before I'm ready to bake.
In a large mixing bowl, combine the sourdough starter, milk, eggs, sugar, vanilla, and melted butter butter. Mix until smooth.
In a separate bowl, combine flour, baking powder, baking soda, cinnamon, and salt. Gradually add the flour mixture to the wet ingredients and mix until a stiff batter forms. Pour the batter into a greased loaf pan.
Mix the brown sugar and cinnamon. Apply generously over the top of the loaf.
Preheat your oven to 350°F . Bake the bread for 50-55 minutes, or until a knife inserted into the center of the bread comes out clean.
