Preheat oven to 350°F (175°C).

Grease and flour a 12-cup Bundt pan.

Sprinkle chopped pecans evenly in the bottom of the pan.

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

In a separate bowl, whisk together milk, orange juice, vegetable oil, eggs, orange zest, and rum.

Make a well in the dry ingredients and add the wet ingredients.

Mix until just combined.

Pour batter into the prepared Bundt pan.

Bake for 60 minutes, or until a wooden skewer inserted into the center comes out clean.

Let the cake cool completely in the pan on a wire rack.

For the glaze, melt butter in a saucepan over medium heat.

Stir in brown sugar and water.

Bring to a boil, then reduce heat and simmer for 5 minutes, stirring constantly.

Remove from heat and stir in rum.

Invert the cake onto a serving plate.

Pierce the top of the cake all over with a skewer.

Pour the glaze slowly and evenly over the cake, allowing it to absorb completely.