Mix together flour, granulated sugar, brown sugar, baking soda, baking powder, salt, cinnamon, and nutmeg
Combine vegetable oil, eggs, and vanilla extract
Mix wet and dry ingredients together
Stir in buttermilk and shredded carrots
Pour batter into prepared pans and bake
For frosting, beat softened butter and cream cheese together
Gradually add powdered sugar and cornstarch
Mix in vanilla extract and salt until smooth
Optionally add salted caramel sauce to filling
Frost cooled cake with cream cheese frosting
