01 -
Preheat the oven to 180°C (350°F). Grease two 9-inch round cake pans with cooking spray and line the bottoms with parchment paper.
02 -
In a medium bowl, whisk together the flour, baking powder, salt, and baking soda.
03 -
In the bowl of a stand mixer fitted with the whisk attachment, beat the ube halaya until smooth. Add the sugar and beat on medium-high speed until combined but not creamed. The mixture should look moist, crumbly, and purple.
04 -
Add the eggs and ube paste and beat on medium speed until combined, about 30 seconds. Add the buttermilk and oil and beat until combined, about 30 seconds more.
05 -
Sift in half of the flour mixture and whisk by hand until just combined. Repeat with the remaining flour mixture and whisk until just combined, being careful not to overmix.
06 -
Divide the batter evenly between the prepared cake pans. Bake until a toothpick inserted into the center comes out clean, 35 to 40 minutes.
07 -
Transfer the pans to a wire rack and let cool for 10 minutes. Run a small offset spatula around the perimeter to loosen the edges. Invert the cakes onto the wire rack. Remove the parchment and invert again so they sit right side up. Let cool completely.
08 -
In the bowl of a stand mixer fitted with the paddle attachment, combine the sour cream, sugar, and salt. Beat on low speed until combined. Add one-third of the coconut and beat on low speed until incorporated. Repeat twice more with remaining coconut.
09 -
Place one cake layer (top side up) on a cake plate. Top with 450 g (2 cups) of frosting and spread evenly. Place the second cake layer on top (bottom side up).
10 -
Cover the top evenly with 560 g (2½ cups) of frosting. Use the remaining frosting for the sides. Wrap the cake with plastic wrap so it touches the frosting directly and protects the cake from air.
11 -
Refrigerate overnight. As it rests, both the cake layers and coconut shreds will absorb excess moisture from the frosting. Let the cake sit at room temperature for 1 hour before serving. Use a serrated knife to slice through the cake.