If you want an extra little kick, take a thawed can of frozen lemonade mix, add just enough water so that it's thin, but it still coats the back of a spoon. While the cakes are still hot, spoon the mixture on top instead of the lemon juice and sugar mixture. You can also pour some in the bottom of your serving dish and let the cake soak it up while it sits.
Preheat the oven to 350 degrees. Grease two 8 1/2 x 4 1/4 x 2 1/2-inch loaf pans.
Cream the butter and 2 cups granulated sugar in the bowl of an electric mixer fitted with the paddle attachment, for about 5 minutes, or until light and fluffy. With the mixer on medium speed, add the eggs, one at a time, and the lemon zest.
Sift together the flour, baking powder, baking soda, and salt in a bowl. In another bowl, combine 1/4 cup lemon juice, the buttermilk, and vanilla. Add the flour and buttermilk mixtures alternately to the batter, beginning and ending with the flour. Divide the batter evenly between the pans, smooth the tops, and bake for 45 minutes to 1 hour, until a cake tester comes out clean.
Combine 1/2 cup granulated sugar with 1/2 cup lemon juice in a small saucepan and cook over low heat until the sugar dissolves.
When the cakes are done, let them cool for 10 minutes, then invert them onto a rack set over a tray, and spoon the lemon syrup over the cakes. Allow the cakes to cool completely.
For the glaze, combine the confectioners' sugar and lemon juice in a bowl, mixing with a wire whisk until smooth. Pour over the top of the cakes and allow the glaze to drizzle down the sides.