Preheat oven to 350 F°. Grease and lightly flour a 12-cup bundt cake pan. Set aside.
In a stand mixer, beat the butter, sugar and lime zest on medium speed until creamy. Beat in the eggs, one at a time and then add lime juice until everything is combined.
In a separate large bowl, combine the flour and baking soda. Gradually add this dry mixture to wet mixture, alternating with the buttermilk.
Pour batter into the prepared bundt pan. Spread out evenly.
Bake for 50 minutes, or until a toothpick inserted in the center comes out clean. Remove cake from oven. Let cake rest for 10 minutes in pan. Take a butte knife and gently loosen the cake around the edges of pan. Then carefully invert the cake onto a cooling rack. Allow the cake to cool completely before pouring on glaze.
Glaze
Whisk together powdered sugar, Key lime juice and milk together until smooth and no lumps remain. When cake is cool, pour glaze all over the top. Garnish with extra lime zest, if desired. Slice, serve and enjoy!
Notes
*If you can't find key limes then you can always use regular limes*