Preheat oven to 350. Grease a loaf pan. Combine topping ingredients in a bowl and mix with fingers to create a crumbly topping, set aside.
Whisk the flour, baking soda and baking powder in a bowl, set aside. Beat the sugar and oil on medium speed to cimbine. Add eggs, one at a time, beating after each addition. Add the mashed bananas and vanilla, beat to combine.
Alternately add the flour mixture and milk, beginning and ending with flour. Beat until the flour is just incorporated.
Spread batter in prepared pan and sprinkle topping evenly over the batter. Bake about 1 hour until a toothpick inserted in the center comes out clean.
To make the glaze, combine butter, water and sugar in a saucepan over medium-high heat and bring to a boil. Immediately reduce heat to medium-low and simmer for 5 minutes.
Remove from heat and stir in the rum. Set aside and cover to keep warm. Cool the cake on a wire rack for 5 minutes. Using a skewer, poke holes all over the top of the bread. Spoon about 1/4C of the glaze over the bread.
Let is sit for a bit to soak in and then pour the remaining glaze over the bread, a little at a time, until it's all absorbed.
