Preheat oven to 350°F (175°C). Grease and flour a 9×13-inch baking pan.

In a bowl, whisk flour, baking powder, and salt.

In a large mixing bowl, beat egg yolks with 3/4 cup sugar until pale and thick. Stir in milk, ube halaya, and ube extract until smooth.

In another bowl, beat egg whites until soft peaks form. Gradually add remaining 1/4 cup sugar and beat until stiff peaks form.

Gently fold egg whites into the yolk mixture, then fold in dry ingredients until just combined.

Pour batter into prepared pan and bake for 25–30 minutes, or until a toothpick inserted comes out clean.

Let cake cool completely. Poke holes all over the cake with a fork.

Whisk together evaporated milk, condensed milk, and heavy cream. Pour evenly over cake, allowing it to soak in. Refrigerate for at least 2 hours.

For topping, beat heavy cream, powdered sugar, and ube extract (if using) until stiff peaks form. Spread over chilled cake before serving.