Preheat the oven to 350°F (175°C) and place the rack in the middle position.

Beat the butter until creamy, then gradually add the sugar and beat until light and fluffy. Add the egg yolks one at a time, mixing well after each addition. (You can use salted butter instead of unsalted for a richer flavor, even with the added salt. The cake will have a subtle savory note that pairs well with the richness.)

Blend the pandan leaves with a little water to extract a concentrated juice. If desired, add pandan extract for a deeper color and stronger aroma, even if the juice is already fragrant.

Sift together the flour, baking powder, and coconut milk powder. With the mixer on the lowest speed, alternately add the dry ingredients and the mixture of pandan juice and milk to the butter mixture, mixing just until combined. Do not overmix, as overbeating with baking powder can make the cake dense.

In a separate, clean, and dry bowl, beat the egg whites with the remaining 1/4 cup (50 grams) sugar until stiff peaks form (the peaks should stand up but bend slightly at the tip). Gently fold the egg whites into the batter.

Line a 8-inch (20 cm) round cake pan with parchment paper. Pour the batter into the pan. Bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean.