Preheat the oven to 350°F (175°C). Grease and flour a 9x13-inch baking pan.

Mix Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

Cream Butter and Sugar: In a large bowl, cream the softened butter and 1 1/2 cups sugar together until light and fluffy (about 3-4 minutes).

Add Eggs and Ube: Add the eggs one at a time, mixing well after each addition. Stir in the 1 teaspoon vanilla extract and ube halaya until fully combined.

Finish Batter: Gradually add the dry ingredients to the wet mixture, alternating with the whole milk. Start and end with the flour mixture. Mix until just combined.

Bake Cake: Pour the batter into the prepared pan and spread evenly. Bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean.

Poke Holes: Once baked, allow the cake to cool in the pan for about 10 minutes. Use a skewer or fork to poke holes all over the top of the cake.

Make Milk Soak: In a separate bowl, mix the evaporated milk and sweetened condensed milk. Pour this mixture evenly over the cooled cake, ensuring it soaks into all the holes.

Chill: Cover the cake and refrigerate for at least 2 hours, or overnight for best results.

Make Whipped Cream: Before serving, whip the 1 cup heavy cream with the powdered sugar and 1 teaspoon vanilla extract until soft peaks form.

Serve: Spread or pipe the whipped cream over the top of the cake. Drizzle with ube extract for color and flavor, if desired.