Prepare Your Oven and Pans: Preheat your oven to 350°F (176°C). Place a rack in the center of the oven. Grease two 9-inch round cake pans thoroughly, then line the bottom of each pan with parchment paper. Grease the parchment paper lightly, or alternatively, grease and dust with flour to prevent sticking.
Mix Dry Ingredients: In a medium bowl, combine the all-purpose flour, baking soda, salt, and ground cinnamon. Whisk well until all ingredients are fully incorporated and the mixture looks uniform.
Combine Wet Ingredients: In a large bowl, whisk together the vegetable oil, granulated sugar, brown sugar, and vanilla extract until smooth and well blended. Add the eggs one at a time, whisking thoroughly after each addition to create a smooth batter.
Incorporate Dry Ingredients: Switch to a rubber spatula and scrape down the sides of the bowl. Gradually add the dry flour mixture to the wet ingredients in three parts, folding gently each time until the flour is fully absorbed and the batter is smooth.
Add Carrots, Nuts, and Raisins: Fold in the grated carrots, chopped pecans, and raisins carefully until evenly distributed throughout the batter, taking care not to overmix.
Bake the Cake: Evenly divide the batter between the two prepared pans. Smooth the tops lightly with a spatula. Bake in the preheated oven for 35 to 45 minutes, or until the cake springs back when lightly pressed and a toothpick inserted into the center comes out clean.
Cool the Cakes: Allow the cakes to rest in their pans for 15 minutes after baking. Then, gently run a knife around the edges and invert the cakes onto wire racks to cool completely. Remove the parchment paper carefully once the cakes have cooled.
Prepare the Frosting: Using a handheld mixer, beat the softened cream cheese in a large bowl on medium speed until smooth and creamy, about one minute. Gradually add the sifted powdered sugar and cornstarch, mixing well after each addition. Pour in the cold heavy cream and beat for 2 to 3 minutes until the frosting thickens and becomes fluffy.
Assemble the Cake: Place one cake layer on your serving plate. Spread a generous layer of frosting evenly on top. Place the second cake layer over it. Spread the remaining frosting on the top of the cake in decorative swirls, leaving the sides bare for a rustic look. Sprinkle the chopped pecans evenly over the frosting as a finishing touch.