Preheat oven to 325°F. Grease a 10-inch bundt pan with shortening and then coat with flour, move flour around for an even coating and discard excess.
In a large bowl or stand mixer, cream together the butter and sugar on medium speed until fluffy. Add eggs and beat well.
In a separate bowl, whisk together the flour, baking soda, and salt. Add the salt to the sugar and butter mixture alternating with the lemonade concentrate and the sour cream. Add lemon zest and vanilla extract and mix until light and fluffy. Pour batter into prepared pan.
Bake for 1 hour, or until a toothpick comes clean from the center. Leave cake in pan and use a skewer to poke small holes throughout the cake.
Butter Glaze
Add butter, sugar, lemonade concentrate, and vanilla to a small pot over medium heat. Stir continuously until butter has melted, do not let boil. Pour glaze over the cake in the pan and allow to set for at least one hour, preferably overnight. Then invert onto a serving dish for serving and dust with powdered sugar, if desired.