1. Prepare the Leche Flan Layer

1. Preheat the oven to 350°F (175°C).
2. In a saucepan, caramelize the sugar for the flan. Heat 1/4 cup of sugar in a small pan over medium heat. Once the sugar begins to melt and turn golden brown, carefully swirl the pan to coat the bottom evenly. Immediately pour the caramel into the bottom of your 9-inch round cake pan, swirling to coat.
3. In a mixing bowl, combine the condensed milk, evaporated milk, eggs, and vanilla. Whisk until smooth.
4. Pour the leche flan mixture into the caramelized cake pan on top of the caramel.
5. Bake for about 45-50 minutes or until the flan is set (you can check by inserting a toothpick—it should come out clean). Allow it to cool completely. After cooling, chill it in the fridge for at least 1 hour.

2. Prepare the Ube Cake

1. In a separate bowl, whisk together the flour, baking powder, and salt. Set aside.
2. In a large mixing bowl, cream together the butter and sugar until light and fluffy.
3. Add the eggs, one at a time, mixing well after each addition. Stir in the ube halaya or ube extract, ube powder (if using), and vanilla extract.
4. Add the dry ingredients to the wet mixture, alternating with the milk. Begin and end with the dry ingredients, mixing gently after each addition until just combined.
5. Pour the ube cake batter over the chilled leche flan layer in the cake pan. Smooth out the top.

3. Bake the Cake

1. Bake the cake for about 35-40 minutes or until a toothpick inserted into the center comes out clean.
2. Let the cake cool in the pan for 15 minutes before flipping it onto a serving platter. The leche flan should be on top, with the ube cake below.

4. Prepare the Caramel Topping

1. In a small saucepan, heat 1/4 cup of sugar and 1 tbsp of water over medium heat. Stir until the sugar melts and turns into a golden caramel.
2. Carefully drizzle the caramel over the top of the cake before serving.