Preheat the oven to 350°F. Grease a baking dish or line it with parchment paper.
In a large mixing bowl, whisk together the pumpkin puree, cane sugar, coconut milk, sweetened condensed milk, melted butter, vanilla extract, and eggs until smooth.
Add sweet rice flour, baking powder, and pumpkin pie spice.
Gradually fold the dry ingredients into the wet mixture, stirring until well incorporated and the batter is smooth.
Pour the batter into the baking dish, spreading it evenly. Bake for 1 hour or until the top is golden brown and a toothpick inserted into the center comes out clean.
Let the cake cool completely before cutting it into squares.