Preheat oven to 350°F and line a 9" loaf pan with parchment paper or lightly spray with nonstick cooking spray.
In a large bowl, mash the bananas with a fork until smooth.
Add the melted butter, sugar, eggs, vanilla extract, and milk. Stir until everything is well combined.
Add the flour, baking soda, and sea salt and mix gently until just combined. Don’t overmix the batter.
Pour the batter into prepared loaf pan.
Bake for 50–60 minutes, or until a toothpick inserted in the center comes out clean. If the top starts to brown too quickly, loosely tent it with foil.
Let the banana bread cool in the pan for 20 minutes, then remove and transfer to a wire rack to cool completely before slicing.
Store banana bread in an airtight container for 3-4 days or freeze for up to 3 months.
Notes
Use very ripe bananas here (serioulsy, black is great). This isn’t the place for barely-yellow ones. The softer they are, the better their flavor, sweetness, and texture will be.
Once you add the flour, mix just until the batter just comes together. Overmixing is how you end up with a dense loaf.
If your oven runs hot (like mine), check it closer to the 50-minute mark. If it needs more time, give it to it, banana bread is forgiving like that.
To check bread for doneness, insert a toothpick (or sharp knife) into the center. If the bread is done, the toothpick will come out with only a few moist crumbs sticking to it.
Mini loaves will bake in less time. Start checking for doneness at 30 minutes.