Preheat oven to 350F. Line 12 muffin cups with muffin liners or spray with nonstick cooking spray.
For the topping: In the bowl of a stand mixer fitted with the paddle attachment, stir together the flour, brown sugar, and cinnamon. Add the butter and toss with a fork to coat with the flour mixture. Mix on medium-low speed until the texture resembles coarse cornmeal, with the butter pieces no larger than small peas. Transfer mixture to a medium bowl and mix in pecans; set aside.
In a medium bowl, whisk together flour, baking soda, and baking powder; Set aside.
4. In the bowl of a stand mixer fitted with the paddle attachment, beat the sugar and vegetable oil on medium speed to combine. Add the eggs, one at a time, beating after each until combined. Add the mashed bananas and vanilla extract; beat to combine. Alternatively add the flour mixture and milk, beginning and ending with the flour. Beat just until the flour is incorporated and finish mixing with a spatula.
Divide batter equally among prepared muffin cups. Sprinkle the streusel mixture over the muffins. Bake until muffin tops are golden and just firm, 22 to 24 minutes, rotating halfway through baking time.
While the muffins are baking, make the rum glaze. In a small saucepan over medium-high heat bring the butter, water, and sugar to a boil. Reduce heat to medium-low and simmer for 5 minutes. Remove from the heat and stir in the rum. Set aside and cover to keep warm.
Cool muffins in muffin tin for 5 minutes. Then, using a toothpick poke holes all over the top of the muffins. Spoon about 1 teaspoon of the rum glaze over each muffin. Let the muffins sit for about 5 minutes then transfer to a wire rack set over a baking sheet. Spoon the remaining glaze over each muffin, about 1 teaspoon for each muffin.