This spice cake is filled with bold flavor from warm Fall baking spices and is topped with a buttery cinnamon streusel. With all this flavor, no one will notice there's sourdough starter discard in it!
Preheat oven to 350 °F. Spray a standard loaf pan with baking spray, and line with parchment paper leaving a 2-inch overhang on the long sides.
Prepare the streusel: Whisk the flour, both sugars, cinnamon, and salt in a small bowl. Cut in the cold butter using a fork or your hands until the mixture resembles pea-sized crumbs. Place the streusel in the refrigerator while you make the batter. It's important to keep the streusel chilled - that keeps it from melting into the batter when the cake is baking.
Prepare the batter: In a large mixing bowl, whisk together flour, sugar, brown sugar, baking soda, salt, and spices. If necessary, mash any large lumps of brown sugar.
Add the sourdough starter, egg, sour cream, canola oil, and vanilla to the flour mixture. Stir together until everything is just combined.
Pour the batter into prepared loaf pan. Top the batter evenly with the streusel, pressing it down gently into the top of the bread so it sticks.
Bake for 45 to 55 minutes, or until a cake tester inserted in the center comes out clean.
Cool the bread in the pan on a wire rack for about 15 minutes, then remove it from the pan using the parchment paper as a sling and allow it to cool completely. Serve & enjoy!
Storage instructions: Sourdough Spice Cake should stay fresh at room temperature for up to 3 days or in the refrigerator for up to a week. For longer storage, you can freeze it for up to 3 months. Allow it to thaw overnight in the refrigerator and bring to room temperature before serving. This cake also makes a great gift and ships well!
You can substitute a scant cup of flour (114 grams) and ½ cup of warm water (118 grams) for the 1 cup of unfed sourdough starter. If desired,You can substitute ¼ cup of applesauce for the canola oil for a lighter bread.One of the benefits of baking quick breads is that they can be baked in different sizes and shapes. You're not limited to a stand loaf. Here are some suggestions for alternative presentations:
One large loaf in a standard loaf pan plus two mini loaves using mini loaf pans. Bake the large loaf for 35 to 40 minutes and the mini loaves for 25 to 30 minutes
Sixmini loaves using mini loaf pans. Bake for for 25 to 30 minutes
Twelve full-size muffins in a standard muffin pan, each well filled ⅔ full. Bake for 18 to 23 minutes