Preheat oven to 350 degrees F. Grease the baking dish with butter and line the bottom with baking paper. Set aside.
Add raisins to a small bowl, top with boiling water and let sit for 10 minutes. Drain well and use paper towels to dry.
In a medium bowl combine dry ingredients: flour, sugar, baking powder, baking soda, cinnamon and salt.
Add wet ingredients to a large bowl: eggs, oil, buttermilk, vanilla extract. Using a hand mixer, whisk on medium speed until fully combined.
Slowly add the dry ingredients, mixing with mixer on low. Stop from time to time to scrape the sides and bottom of the bowl. Whisk just until fully combined.
Stir in shredded carrots, chopped walnuts, and raisins.
Transfer to the baking dish and bake for 20-25 minutes or until a toothpick inserted in the middle comes out clean.
Remove the cake from the oven and run a knife around the edges to loosen from the pan. Let it cool in the pan for about 30 minutes. Invert the cake onto a plate and then re-invert onto another plate. Cool completely before frosting.
Prepare the Cream Cheese Frosting according to recipe directions.
Cover the top of the cake with the frosting.
Use chopped walnuts and cinnamon to garnish.
Refrigerate for at least 2-3 hours, or until somewhat stiff before cutting into squares/bars and serving.