First, boil water in your steamer over medium-high heat. While waiting, brush your kutsinta molds lightly with cooking oil. Cover your steamer lid with a clean kitchen cloth to prevent water drops from falling on the cakes.
Mix your dry ingredients in a large bowl - sift the rice flour, all-purpose flour, and brown sugar together until well combined with no lumps.
In a small bowl, mix the annatto powder with 3 tablespoons of hot water. Stir until the powder completely dissolves and turns bright orange-red.
Slowly pour the water into your flour mixture while whisking. Keep whisking as you add the dissolved annatto and lye water. Mix until your batter is smooth and even in color - it should look like pancake batter.
Fill each mold about ¾ full with your batter. Don't fill to the top as the kutsinta will rise while steaming.
Put the filled molds in your steamer. Steam for 45 minutes over medium-high heat. You'll know they're done when you stick a toothpick in the center and it comes out clean. The surface should feel firm but springy.
Let them cool for 2-3 minutes in the molds. Gently loosen the edges with a butter knife and remove from molds.
Serve your kutsinta warm with plenty of freshly grated coconut on top.
Best eaten fresh, but you can keep leftovers in a covered container at room temperature for a day. To reheat, just steam for 2-3 minutes until warm.
Remember: If your batter looks too thick, add a little water. If it's too thin, add a bit more rice flour. The perfect batter should slowly drip off your whisk, like honey.