Bring about 1-1/2 inches of water to boil in a steamer fitted with a basket large enough for a 9-inch square baking dish to lie flat.
Sift the tapioca flour, rice flour, and arrowroot powder together into a bowl. Gradually stir the coconut cream into the mixture until completely incorporated and smooth, about 10 minutes. Stir the sugar, pumpkin, coconut milk, and salt into the mixture, dissolving the sugar completely into the batter; pour into a 9-inch square baking dish.
Steam over the boiling water until the cake is cooked through, about 25 minutes. Allow the cake to cool before cutting into squares to serve.