Preheat oven to 350 F. Grease and flour a 12-cup bundt pan. In a medium bowl, whisk together flour, baking powder and salt.
In the bowl of a stand mixer (or use a hand-held mixer), beat butter on medium-high speed until it is smooth. Add sugar and beat for 2-3 minutes until the mixture is fluffy.
Reduce speed and add eggs one at a time, mixing well after each addition. Add the vanilla extract and mix. Add the flour and milk alternately beginning and ending with the flour and incorporating after each addition. You should have added the flour 3 times and the milk two times. Do not overmix.
Scoop out 1/2 of the dough into another bowl. Add ube extract to one bowl and fold until the color is uniform. You have two flavored batters now- vanilla and ube.
ALternate scooping the batters into the bundt pan until they are all used up. Smoothen the top with an angled spatula. Bake in the preheated oven for 4-50 minutes, or until a skewer or a knife inserted at the center of the cake comes out clean. The cake will have a crackly top. Let cool on a wire rack completely.
Turn the cake over on a serving plate. Dust with icing sugar.