Preheat the oven to 170°C (340°F) and grease the cake pan.

Melt the margarine in a saucepan, then set it aside to cool.

Cook the granulated sugar in a saucepan until it becomes a deep amber caramel.

Carefully pour in the hot water, then stir until the caramel dissolves.

Add the pandan leaves and cinnamon stick, then simmer the caramel syrup for 5 min.

Remove the pandan leaves and cinnamon stick, then cool the caramel syrup completely.

Sift the wheat flour, tapioca starch, baking powder, baking soda, and salt into a mixing bowl.

Whisk the eggs, sweetened condensed milk, and liquid vanilla extract in a second bowl.

Add one portion of the flour mixture to the egg mixture, then stir in one portion of cooled caramel syrup.

Repeat the alternating additions until both mixtures are incorporated, then stir consistently in one direction.

Pour in the cooled melted margarine, then stir in one direction until the batter is smooth and bubbly.

Pour the batter into the prepared cake pan, then gently tap the pan to release large air bubbles.

Bake the cake for 45 min until set and deeply browned.

Cool the cake in the pan for 15 min, then transfer it to a cooling rack before slicing.