Dairy-Free "Nuttercream" Frosting

One of the reasons I hate buying grocery store cakes is the frosting. It's typically shortening-based and not nearly as good as homemade. Like, not even close. I'd rather have good-tasting than good-looking frosting. Even though we couldn’t have dairy — so no butter and no milk, both of which I'd normally put in my frosting — my son could now have nuts, so here’s my alternative to traditional buttercream frosting.