Preheat the oven to 350°F (180°C). Line a 20cm (8-inch) round baking tin with parchment paper.
Pour the batter into the tin, and place it inside a larger pan with water about 2cm (3/4 inch) high.
Bake at 350°F (180°C) for 40 minutes, then reduce to 320°F (160°C) for 10 minutes until the cake rises and turns golden.
Turn off the oven, leave the cake inside for an hour, then let it cool to room temperature.
Refrigerate the cake for several hours or overnight.