Preheat oven to 350 degrees F. Grease and flour a 10" fluted tube pan. In a large bowl, cream butter, sugar and zest until light and fluffy, 5-7 minutes. Add juice and vanilla, and mix on high for 1 minute. Add eggs, 1 at a time, on low speed just until yellow disappears. Scrape down bowl as needed and between each addition. Sift flour and salt together into clean bowl. Add 1/3 of the flour mixture alternately with 1/2 of the milk, on low speed until just mixed, beginning and ending with flour. Transfer to prepared pan.
Bake until a toothpick inserted in center comes out clean or with a moist crumb, 1 1/4 to 1 1/2 hours. cool in pan 10 minutes before removing to a wire rack to cool completely.
For frosting, in a large bowl, beat cream cheese, butter, lime zest and lime juice until smooth. Gradually beat in confectioners' sugar. Spread over cake. If desired, garnish with lime slices and additional zest.
Notes
To remove the cake easily, use solid shortening to grease plain and fluted tube pans.