Preheat the oven to 325 degrees F (165 degrees C). Grease and flour a 10 or 12-cup bundt pan.
In a medium bowl, stir together the flour, baking powder, and salt. Set aside.
In the bowl of a stand mixer or using a large bowl with a hand mixer, beat the butter and sugar together until light and fluffy. This will take about 5 minutes. Add the eggs one at a time, incorporating each before adding the next.
Add the extracts, key lime zest, and key lime juice. Stir just until combined.
Beat the flour mixture into the butter mixture, alternating with the 1 cup of milk. Finish with the dry ingredients. Mix until you have a smooth batter and there are no streaks of flour. Make sure you reach the bottom of the bowl.
Pour or spoon the batter into the prepared bundt pan. Smooth the top of the batter and bake for 60 minutes on the middle rack, or until a toothpick comes out clean.
Cool cake on a wire rack for about 10-15 minutes before removing from the pan. After removing the cake from the pan, allow the cake to cool completely before decorating with the icing.