Preheat your oven to 350°F (175°C) and position a rack in the center

Thoroughly grease two 9×5-inch loaf pans with butter or baking spray, then dust lightly with flour, tapping out any excess

In a medium bowl, whisk together the flour, baking powder, and salt until well combined; set aside

In the bowl of a stand mixer fitted with the paddle attachment (or using a hand mixer), beat the butter on medium speed until creamy, about 1 minute

Gradually add the sugar and continue beating on medium-high speed until the mixture is pale and fluffy, about 4-5 minutes

Add the lime zest and beat for 30 seconds to release the oils

Add the eggs one at a time, beating well after each addition and scraping down the sides of the bowl as needed

Beat in the lime juice until incorporated

Reduce the mixer speed to low and add the flour mixture in three portions, alternating with the milk (beginning and ending with the flour mixture)

Mix just until each addition is incorporated, being careful not to overmix

Divide the batter evenly between the prepared loaf pans and smooth the tops with a spatula

Bake in the preheated oven for 55-60 minutes, or until a wooden toothpick inserted into the center comes out clean or with a few moist crumbs

If the tops begin to brown too quickly, loosely cover with aluminum foil during the last 15 minutes of baking

Allow the cakes to cool in the pans for 20 minutes

Carefully run a knife around the edges of the pans to loosen the cakes, then invert onto a wire rack

Turn the cakes right side up and allow to cool completely, about 2 hours

Once the cakes are completely cool, prepare the glaze by whisking together the confectioners' sugar, 2 tablespoons of milk, lime zest, and lime juice (if using) in a medium bowl

Add additional milk, 1 teaspoon at a time, until the glaze reaches a pourable but still thick consistency

Place the cooled cakes on a wire rack set over a baking sheet or piece of parchment paper to catch drips

Pour or spoon the glaze evenly over the tops of the cakes, allowing it to drip down the sides

Let the glaze set for about 30 minutes before slicing and serving