Place the springform pan / tube / bundt cake pan / in the oven. Preheat the oven to °325 F
Add coconut milk, water (coconut milk), and sugar to a small pot over low heat. Stir until dissolved
Remove coconut syrup from the heat and allow to cool to room temperature
Sift the tapioca starch and rice flour into a medium bowl
Make single acting baking powder - in a small bowl, combine the cream of tartar and baking soda to make the single-acting baking powder
Add eggs, oil, and vanilla extract to a large bowl. Gently whisk everything together for 1 minute. Avoid whipping or beating the eggs as this introduces air in the egg mixture
Combine the coconut syrup and egg mixture - whisk together gently
Add half of the sifted flour mixture and mix together until mostly combined
Add the remaining flour mixture and continue whisking gently. The batter will be lumpy at first, but keep slowly whisking (2-3 minutes) until the lumps dissolve
Add the pandan paste and blend well. (There will still be some small lumps in the batter.)
Add the single-acting baking powder and whisk until combined (1 minute). *Note the batter becomes foamy as it reacts with the baking powder. Now that it's activated you'll want to work quickly to get the cake into the oven.
Remove the hot pan from the oven and spray with a generous amount of non-stick cooking spray
Using a strainer add the batter into the baking pan - use a whisk to break-down any remaining lumps
Bake for 30-35 minutes. Insert a toothpick into the center of the cake to check when it's done - toothpick will be clean when the cake is done.
Remove from oven and allow to cool before serving