Preheat oven to 350°F. Place 12 cupcake liners in cupcake tray.
Combine sugar, vegetable oil, condensed milk, buttermilk, and 2 large eggs in a large bowl. Whisk until well combined.
Add the ube halaya to the mixture. Whisk until creamy with no lumps. Add the ube extract and whisk until fully incorporated.
Sift the cake flour, baking powder, and salt on top of the mixture. Important: Stir gently until just combined. Do not overmix.
Fill the cupcake liners with the batter until 2/3 full. Do not overfill.
Bake for 15 minutes until a toothpick inserted in the center pulls out clean. Let the cupcakes cool for 1 minute in the cupcake tray before transferring to a wire rack to cool completely before frosting.