In a large bowl, combine the rhubarb, sugar, nutmeg, lemon juice, salt, flour, and tapioca, and mix until the rhubarb looks like it’s coated with coarse wet sand, about 2 minutes. [Editor’s Note: If using thawed frozen rhubarb, gently but firmly press it with paper towels to remove as much liquid as possible prior to tossing it with the other ingredients.]