Preheat oven to 325°F. Grease and flour a 10-inch Bundt pan.
Beat butter and sugar until light and fluffy, about 3–5 minutes.
Add eggs one at a time, mixing well after each addition.
Whisk together flour, baking powder, and salt.
Alternate adding the dry ingredients and sour cream, mixing just until combined.
Stir in Key lime juice, lime zest, and vanilla extract.
Pour batter into the prepared pan and bake for 75–90 minutes, or until a toothpick comes out clean.
Cool in the pan for 15 minutes, then transfer to a wire rack to cool completely.
Whisk powdered sugar and Key lime juice until smooth to make the glaze.
Drizzle glaze over the cooled cake, let set, then slice and serve.
