Preheat the oven to 400˚F.
Grease 2 (9-by-2-inch) cake pans, line the bottoms with oil and add paper. Grease paper.
In the bowl of an electric mixer fitted with the paddle attachment, beat the sugar, oil, and eggs on medium~high speed for 2 minutes, until light yellow and thickened. Stir in the vanilla.
In another bowl, sift together the 2 cups of flour, cinnamon, baking soda, and salt. With the mixer on low, slowly add the dry ingredients to the wet ones.
In a medium bowl, toss the carrots, raisins, pistachios, and the 1 tablespoon of flour. Stir into the batter with a rubber spatula.
Divide the batter into the 2 cake pans and smooth the tops. Bake for 10 minutes, lower the temperature to 350˚F. and bake for 30~35 minutes, until a toothpick comes out clean. Cool in the pans for 15 minutes, then turn out onto a cooling rack and cool completely.
Place one cake layer on a flat serving plate, rounded side down. Spread half the frosting on the top (but not the sides). Place the second cake layer on top of the first cake layer, rounded side up. (If the cake top is too rounded, use a serrated knife to level it.) Frost just the top of the cake.
Sprinkle the finely chopped pistachios on the top of the cake for garnish.