Preheat oven to 350 degrees. Line a loaf pan with parchment paper and set aside.
Add flour, ¾ cup pecans, baking soda, cinnamon, nutmeg, and sea salt to a bowl and whisk until uniform, ensuring the pecans get coated with the flour mixture. This step prevents the pecans from clustering or sinking into the bottom of the batter while baking.
Peel bananas and add them to another bowl. Smash them into a kind of paste consistency then add egg, brown sugar, milk, melted butter, rum, and vanilla extract, and mix until combined.
Add wet banana mixture to dry flour mixture and stir until just combined. There will likely be bits of flour around the pecans and that's ok. Don't overmix the batter. Transfer batter to prepared loaf pan.
Chop remaining ¼ cup of pecans into pieces and pour over top of the batter. Gently press the pecan pieces into the batter so that they stick to the bread.
Place pan into oven and bake on center rack for about 40-50 minutes or until top of loaf is golden brown and a toothpick inserted in the loaf comes out clean.