Preheat oven to 350⁰F. You will need two nine-inch cake pans sprayed with non-stick cooking spray (such as PAM®) and lined with a circle of baking parchment paper.
In a large mixing bowl beat together the oil, brown sugar and eggs. Stir in the grated carrots, raisins, walnuts, and orange extract. Sift together the flour, baking soda, cinnamon, and nutmeg and stir into the carrot mixture until blended and smooth. Split the mixture between the two prepared pans and bake for approximately 40–50 minutes, or until a knife inserted comes out clean. When done, remove from the oven and cool on a rack for 15–20 minutes before turning out to completely cool. Chill in the refrigerator overnight before icing.
Mix the cream cheese and butter until smooth in a bowl with a beater. Add in the vanilla. Mix in the sifted powdered sugar and mix until blended. Split the cakes, then fill and ice them. If you have extra walnuts, put them on the outside of the cake. Chill before serving.