Place the oven rack in the middle position of the oven. Preheat the oven to 350 degrees F. Coat three 7-inch cake pans with vegetable spray. Line the bottoms with parchment paper cut to fit and coat parchment paper with vegetable spray. Dust the pans with flour and tap out the excess.
To make the cake: In a large bowl, sift together the flour, cocoa powder, and salt.
In the bowl of a stand mixer, add the shortening and sugar. Using the paddle attachment, cream them together until the mixture is light and the sugar is dissolved. Add the eggs one at a time and mix. Add the food coloring and mix. Pour the vanilla into the buttermilk. On low speed, add the dry ingredients to the batter alternately with the buttermilk, beating after each addition. Mix the baking soda into the vinegar and fold that into the batter.
Divide the batter evenly among the prepared pans and bake for 30 to 35 minutes, or until a toothpick inserted into middle of cake comes out clean. Place the pans on a rack and allow them to cool for 20 minutes. Run a butter knife gently around the edges and invert the cakes onto a second rack. Let the cakes cool completely.
To make the frosting: In the bowl of a stand mixer fitted with the paddle attachment, add the cream cheese and butter and beat until they are completely combined. On low speed, gradually add the confectioners' sugar 1 cup at a time, then beat at highest speed until thick and creamy. Add the vanilla and salt to the mixture and beat until combined.
To frost the cake: Level the cakes by slicing off the rounded tops. Using a pastry brush, brush the crumbs off the cake and place the bottom layer on a cake round lined around the edges with 4 small pieces of waxed paper. Using an offset spatula, spread some of the frosting over the top of this layer, leaving a 1-inch border. Set the middle layer, bottom-side up, and frost the top, leaving a 1-inch border. Cook's Note: Place the middle and top layers of the cake, bottom-side up to prevent the crumbs from mingling with frosting.
Add the third cake layer bottom-side up, and frost the top and sides to coat completely. Immediately cover the sides of the cake with chopped pecans, if using. Gently remove the pieces of waxed paper from under the bottom cake layer. Refrigerate the cake until ready to serve. Store the leftover cake in a refrigerator loosely wrapped in waxed paper.
NotesTo decorate cake, set red raspberries on top of the cake alternating with toasted pecan halves.