1. 1. Combine Wet Ingredients: In a large mixing bowl, whisk together the unfed sourdough discard, melted butter, light brown sugar, eggs, and vanilla extract until the mixture is smooth and well combined.

2. 2. Add Dry Ingredients: In a separate medium bowl, whisk together the all-purpose flour, baking soda, and salt. Make sure these dry ingredients are thoroughly mixed to ensure even distribution throughout the batter.

3. 3. Combine Wet and Dry: Gradually add the dry ingredient mixture to the wet ingredient mixture, stirring gently with a spatula or wooden spoon until just combined. Be careful not to overmix; a few small lumps are perfectly fine.

4. 4. Initial Rest Period: Cover the bowl with plastic wrap or a clean kitchen towel and let the batter rest at room temperature for 6-7 hours. This extended rest allows the sourdough discard to slightly leaven the batter and develop a richer flavor.

5. 5. Prepare for Baking: After the resting period, preheat your oven to 350 F (175 C). Grease and flour a 9×5 inch loaf pan, or line it with parchment paper. If using the optional topping, mix the granulated sugar and ground cinnamon in a small bowl.

6. 6. Fill and Top: Pour the batter into the prepared loaf pan, spreading it evenly. If using the cinnamon sugar topping, sprinkle it generously over the top of the batter.

7. 7. Bake the Loaf: Bake for 45-55 minutes, or until a wooden skewer or toothpick inserted into the center of the loaf comes out clean. The top should be golden brown and firm to the touch.

8. 8. Cool and Serve: Once baked, remove the loaf from the oven and let it cool in the pan for about 10-15 minutes before carefully lifting it out onto a wire rack to cool completely.