Preheat the oven to 350°F (176°C) and prepare two 8-inch round cake pans by greasing them with oil and dusting with flour.

Whisk together the all-purpose flour, ground cinnamon, salt, and baking soda in a medium mixing bowl.

In a large bowl, whisk together the eggs, granulated sugar, vanilla extract, sourdough discard, and vegetable oil until smooth.

Fold the dry ingredient mixture into the wet ingredients until no dry flour remains.

Gently fold in the grated carrots, raisins, and chopped nuts.

Divide the batter between the prepared cake pans and bake for 35–40 minutes until a toothpick comes out clean.

Cool the cakes in the pans for 20 minutes before transferring to a wire rack to cool completely.

Prepare the brown butter by heating it in a saucepan until golden brown and nutty.

In a bowl, beat together the cooled brown butter, cream cheese, and vanilla extract, then sift in powdered sugar and mix until fluffy.

Once cooled, frost the first layer of cake, add the second layer, and frost the top and sides.

Refrigerate the cake for about 30 minutes to allow the frosting to set.

Slice and serve the cake with coffee or tea.