• Preheat your oven to 180c/350f.

 Make the Caramel Layer

• In a pot or pan, add sugar.
• Place on medium heat and keep heating and stirring until the sugar melts and turns amber.
• Pour the caramel into an 8-inch cake tin and set it at room temperature.
• Do not grease the tin; an un-greased tin helps the cake rise better.

Make the Flan

• In a large bowl, combine all the ingredients for the flan.
• Whisk the ingredients together.
• Pour the mixture through a sieve into the tin on the caramel layer.
• Ensure the sugar has set before pouring the flan mixture.
• Set it aside while preparing the cake batter.

Make the Cake Batte

• In a large, clean bowl, add egg whites and cream of tartar.
• Begin whipping until the mixture becomes foamy.
• Gradually add sugar, slowly whipping until you achieve stiff peaks.
• Mix egg yolks and sugar in a separate large bowl until the egg yolks lighten in color and the mixture slightly increases in volume.
• Add oil, water, and ube extract and whisk until combined.
• Add flour and baking powder and mix until combined.
• Gently fold in half of the whipped egg whites, followed by the rest, ensuring no lumps or streaks of egg whites remain.

Bake the Cake

• Place the tin in a baking/roasting tray with high sides.
• Pour boiling water into the large tray until it reaches halfway up the sides of the tin.
• Carefully place this in the oven and bake at 180c/350f for about 55-60 minutes, until a toothpick inserted into the cake comes clean. The cake will be jiggly due to the flan; this will set as it cools.
• Remove from the oven, let it cool completely, then refrigerate overnight.
• Take it out of the tin the next day, cut it into slices, and enjoy!