Carrot Cake with Cream Cheese Frosting

Position a rack in the middle of the oven and preheat to 375 °F. Butter the bottom and sides of 2 (9-inch-round, 2-inch-deep) cake pans and line the bottoms with parchment paper. In a large bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, nutmeg, and allspice. In the bowl of a stand mixer fitted with the paddle attachment, mix the brown sugar on the lowest speed to break up any lumps. Add 1 egg and continue to mix on low until smooth and incorporated. Add the remaining eggs, one at a time, and mix on low until smooth and incorporated. Shut off the mixer and scrape down the bowl and paddle. Return the mixer to low then add the oil in a thin steady stream and continue to beat until fully incorporated. Add the flour mixture in 3 batches, using a large rubber spatula to fold the mixture together until just incorporated. Fold in the carrots, along with the nuts and raisins, if using. Divide the batter between the prepared pans and smooth the tops. Bake until the layers are firm and risen and the tip of a paring knife inserted in the center of the cake emerges clean, about 40 minutes. Transfer to a wire rack to let cool for 5 minutes then invert the cake layers onto the rack and peel off the parchment paper. Use another rack or a large plate to invert the cake layers again then slide them back on to the rack so they are right side up. Let the cake layers cool completely. DO AHEAD: The cakes can be baked ahead, cooled, wrapped in a double layer of plastic wrap, and refrigerated for up to 2 days, or frozen up to 1 month.