A soft and fluffy Filipino-inspired ube cake made with rich ube halaya, coconut milk, and creamy ube buttercream. Its beautiful purple color, delicate sweetness, and smooth purple yam flavor make it a comforting yet eye-catching dessert for celebrations, afternoon tea, or special occasions.
Preheat the oven to 350°F (175°C). Grease two 8-inch (20 cm) round cake pans with a little of the cake butter and line the bottoms with parchment paper. In one bowl, whisk together the flour, baking powder, and salt. In another bowl, combine the ube halaya, whole milk, coconut milk, ube extract, and vanilla extract until smooth and evenly blended.
In a large mixing bowl, beat the remaining softened cake butter and granulated sugar for 3–4 minutes until pale, light, and fluffy. Add the eggs one at a time, mixing well after each addition and scraping down the bowl. Alternate adding the dry ingredients in three additions and the ube mixture in two additions, beginning and ending with the dry ingredients. Mix on low only until the batter is smooth and evenly purple; do not overmix.
Divide the batter evenly between the prepared cake pans and smooth the tops. Bake for 25–30 minutes, until the cakes are risen, the centers spring back lightly, and a toothpick inserted into the center comes out clean. Cool in the pans for 10 minutes, then carefully turn the layers out, remove the parchment, and transfer them to a wire rack. Let them cool completely before adding buttercream.
Beat the softened butter for the buttercream until smooth and creamy. Gradually add the powdered sugar on low speed, then beat until light. Add the ube halaya, ube extract, and salt. Add the milk one tablespoon at a time, using only enough to create a smooth, fluffy, and spreadable buttercream. Scrape down the bowl and mix until the color and texture are even.
Place one completely cooled cake layer on a serving plate or cake board. Spread an even layer of ube buttercream across the surface, then place the second cake layer on top. Cover the top and sides with a thin crumb coat, then use the remaining buttercream to finish and smooth the frosting. Keep the presentation simple so the purple cake layers and ube buttercream remain the main visual focus. Slice into 8 servings.
