Preheat your oven to 350°F (175°C) and prepare an 8.5x4.5 inch loaf pan by greasing it and lining it with parchment paper.

In a large bowl, whisk together granulated sugar, dark brown sugar, and oil until combined. Beat in the eggs one at a time until thickened.

In another bowl, sift together the flour, baking powder, baking soda, spices, and salt.

Gradually fold half of the dry mixture into the wet ingredients, then mix in sour cream and vanilla until just combined.

Add the remaining dry ingredients and fold in grated carrots until no dry spots remain.

Pour the batter into the prepared loaf pan and bake for 65-75 minutes or until a toothpick inserted comes out clean.

Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

To prepare the frosting, cream softened butter, then gradually add cream cheese, powdered sugar, and vanilla extract, mixing until smooth.

Frost the cooled cake generously and garnish with toppings like chopped walnuts or cinnamon if desired.