Preheat your oven to 350°F (175°C) and grease a 9x5 inch loaf pan with butter or non-stick spray.

Cream together 1 cup of granulated sugar and ½ cup of unsalted butter using an electric mixer on medium speed for about 3-5 minutes.

Add 3 large eggs to the creamed mixture, one at a time, mixing well for about 30 seconds after each addition.

In a separate bowl, whisk together 2 cups of all-purpose flour and 2 teaspoons of baking powder. Gradually add this mixture to the butter mixture, alternating with ½ cup of fresh key lime juice.

Fold in the zest of 3 key limes into the batter ensuring it's evenly spread.

Pour the prepared batter into the greased loaf pan, smoothing the top with a spatula.

Bake for 50-60 minutes, until a toothpick inserted comes out clean.

Let the cake cool in the pan for about 10 minutes before transferring to a wire rack.

Whisk together 1 cup of powdered sugar and enough fresh key lime juice to achieve a smooth, pourable consistency.

Drizzle the glaze over the cooled cake, allowing it to cascade down the sides.