Preheat oven to 350 degrees F.
Sift the baking powder, salt, flour, and cocoa together. Set aside.
Set up a mixer with a paddle attachment. On low to medium speed, add oil, then sugar then eggs and vanilla. When eggs are fully incorporated, alternately add flour mixture and water. Batter should be smooth, and on the thin side.
Spray bundt pan thoroughly. Add batter to pan and bake for 1 hour.
While baking, melt together all ingredients in rum glaze. Do not boil.
Once cake is baked, remove from oven and set on a baking rack, do not remove from bundt pan.
Pour/brush rum glaze over the warm cake. It is best to do this when cake is still warm so rum can absorb into the cake. Pour/brush rum glaze until completely gone, this will take a while. If you feel cake cannot take anymore glaze, walk away for 10 minutes, come back and continue to pour/brush. The cake will have had time to absorb and will be able to take on more glaze.
Completely cool the cake for 1 to 2 hours in the fridge before taking out of bundt pan. You’re trying to cool that glaze into the cake completely.
Next, make the lime glaze. This will be the frosting going ontop of the cake.
Sift powdered sugar into a bowl, add lime zest, and corn syrup. Start whisking and add milk, then add rum. Once combined, you should have a nice drippy consistency.
Once cake is completely cooled, invert onto plate or cake stand. If you have problems removing the cake from the pan, don’t panic. Invert the cake pan onto whatever you’d like, then either use a torch or a blow dryer and heat the sides of the pan until the cake releases.
Spoon or pipe glaze onto cake.