Preheat your oven to 350°F (175°C). Grease a loaf pan with butter or cooking spray and sprinkle flour over it.

In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside.

In a large bowl, cream the unsalted butter and granulated sugar until light and fluffy, about 3 to 5 minutes.

Add the eggs one at a time, mixing well for about 20 seconds after each addition.

Stir in fresh key lime juice, lime zest, and vanilla extract into the egg mixture until combined.

Gradually add the dry ingredients to the wet mixture, folding until just combined.

Pour the batter into the greased loaf pan and bake for 50-60 minutes until a toothpick comes out clean.

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

Whisk together powdered sugar and key lime juice to create a glaze, then drizzle over the cooled cake.