Preheat the oven to 350℉. Grease and flour a 9x9-inch baking pan*, then set aside.

In a small bowl, whisk together the flour, baking soda, baking powder, cinnamon, ginger, cloves, nutmeg, and salt. Set aside.

Peel and shred your carrots using the small holes of a box grater. Set aside.

In a large bowl, use a hand-held mixer to mix together the sugars, oil, eggs, and vanilla extract until smooth and fluffy, about 1 minute. Add the sourdough discard and mix until smooth. Fold the dry ingredients into the wet ingredients and mix until just combined and no dry spots remain. Fold in the carrots, nuts and raisins and mix until just combined. Transfer your batter to the prepared baking pan.

Bake for 45-50 minutes or until a toothpick inserted in the center of the cake comes out clean. Let the cake cool in the pan for about 15 minutes, then transfer to a cooling rack to cool fully.

After the cake has cooled, make the frosting. In a medium bowl, whip the butter with a hand-held mixer until smooth and creamy, about 2-3 minutes. Add the sour cream and vanilla extract, and mix until smooth. Add the powdered sugar and mix until smooth. If the icing seems too thick, add more sour cream (1 Tablespoon at a time) to reach a thinner consistency.

Transfer the cooled cake to a serving plate or board, then spread the cake with the frosting. Slice and serve!