Preheat oven to 325°F (163°C). Grease and flour a 10-inch Bundt pan.

In a medium bowl, whisk together flour, baking powder, and salt.

In a large bowl, cream butter and sugar until light and fluffy.

Add eggs one at a time, beating well after each addition. Stir in vanilla extract.

Alternately add dry ingredients and milk to the butter mixture, beginning and ending with dry ingredients. Mix until just combined.

Stir in dark rum until batter is smooth.

Pour batter into prepared pan and smooth the top.

Bake for 60-70 minutes, or until a toothpick inserted into the center comes out clean.

While the cake bakes, prepare the rum syrup: Combine sugar, water, and rum in a saucepan. Bring to a boil, then reduce heat and simmer for 5 minutes.

Remove cake from oven and let cool in the pan for 10 minutes. Poke holes in the cake and slowly pour warm rum syrup over it.

Allow cake to cool completely in the pan before inverting onto a serving plate. Dust with powdered sugar and brush with additional rum if desired.