Preheat oven to 325°F (165°C). Grease and flour a 10-inch (12-cup) tube or Bundt pan.
Cream butter and shortening together on medium speed until smooth and creamy.
Gradually add sugar, beating until light and fluffy.
Add eggs one at a time, beating just until blended after each addition.
In a separate bowl, stir together flour, baking powder, and salt.
Alternate adding flour mixture and milk to the creamed mixture, beginning and ending with the flour. Mix on low speed just until blended.
Stir in vanilla, lime zest, and key lime juice until fully incorporated.
Pour batter into prepared pan and smooth the top.
Bake at 325°F for 1 hour 15 minutes to 1 hour 20 minutes, or until a toothpick inserted in the center comes out clean.
Cool in the pan on a wire rack for 10–15 minutes.
Meanwhile, prepare the glaze by whisking together powdered sugar, key lime juice, and vanilla extract.
Remove cake from the pan and immediately brush the glaze over the warm cake.
Let the cake cool completely for about 1 hour before serving.
Tips
For convenience, use bottled key lime juice like Nellie and Joe’s.
Zest the limes before juicing for best results.
Serve with whipped cream or fresh berries for an elegant touch.
