Preheat your oven to 325°F (165°C). Grease and flour a bundt pan or tube pan thoroughly and set aside.
In a large mixing bowl, beat the butter and shortening together until smooth and creamy. Add the sugar gradually, beating until light and fluffy, about 4–5 minutes.
Add the eggs one at a time, beating well after each addition to fully incorporate.
In a separate bowl, sift together the flour, baking powder, and salt.
Add the dry ingredients to the creamed mixture alternately with the milk, starting and ending with the flour. Mix until just combined.
Stir in the vanilla extract, lime zest, and key lime juice until evenly distributed.
Pour the batter into the prepared pan and smooth the top. Bake for 1 hour and 15 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan for 15 minutes, then turn it out onto a wire rack to cool completely.
In a small bowl, whisk together the powdered sugar, key lime juice, and vanilla extract until smooth.
Drizzle the glaze over the cooled cake. Let it set before slicing and serving.
Enjoy!