1) Preheat the oven to 350°F. Grease two parchment-lined 8" round cake pans; one 9" x 13" rectangular pan; or the wells of one muffin tin (12 muffin cups). Or line the muffin tins with papers, and spray the insides of the papers.
2) Beat together the oil, eggs, carrots, and spices.
3) Whisk the cake mix with the baking soda; stir into the bowl with the wet ingredients.
4) Add the raisins, nuts, and pineapple (if you're using it). Mix until blended.
5) Spoon (or pour) the batter into the prepared pan(s).
6) Bake the cake layers for 60 minutes; the 9" x 13" pan for 50 minutes; or cupcakes for 30 minutes. The cake should be brown and firm on top, with an internal temperature of 212°F.
7) Remove the cake(s) or cupcakes from the oven, and allow to rest for 5 minutes before turning out of the pan onto a rack to cool. Frost when completely cool.
8) To make the frosting: Beat the butter and cream cheese together until smooth.
9) Add the salt and vanilla; beat in the sugar.
10) Beat in an additional teaspoon of milk or cream if the frosting is too stiff to spread; beat in more sugar if it's too thin.
11) Spread the frosting over the cake layers and stack them, then frost to cover; or spread frosting onto the 9" x 13" cake, or onto the cupcakes.
Yield: two 8" rounds; one 9" x 13" cake; or 24 cupcakes.