Preheat your oven to 350˚F.
Use a little bit of avocado or coconut oil to grease your baking dish.
Grate the carrots with a box grater or a food processor and set them aside.
In a large mixing combine the flour, baking powder, cinnamon, salt. Mix these ingredients well.
To this bowl or a separate large mixing bowl, the eggs, vanilla extract, maple syrup, avocado oil, sourdough starter, and the shredded carrots. Optional: add chopped walnuts. Mix until all the ingredients are well-incorporated.
Pour the cake batter into the greased baking dish.
Bake the sourdough carrot cake for about 55 - 90 minutes or until an inserted knife or toothpick comes out clean.
Let the cake cool down on a wire rack at room temperature before frosting.
Let the cream cheese and maple come to room temperature and put them into a medium bowl. Add the vanilla extract.
Either with your stand mixer or a handheld mixer, whip the frosting until it is very soft and uniform.
Spread the frosting on the cooled cake.
This sourdough carrot cake will taste even better the next day!