FOR THE CAKE

1. Grease a 16.5 x 11.38 sheet pan and set aside.
2. Preheat oven to 350 degrees and adjust the rack to the middle position.
3. In a large pot, melt the butter over medium heat.
4. Add the water and the lemon juice, increase the heat to high, and bring to a boil. Immediately remove the pot from the heat and allow to cool for at least 5 to 10 minutes. 
5. Whisk in the flour until smooth, followed by the sugar, sour cream, and lemon zest. Do not over beat, just mix until combined.
6. Whisk in eggs one at a time until well blended.
7. Mix in the vanilla extract, and then sprinkle the baking soda and salt over the top of the batter and whisk until all ingredients are well blended.
8. Pour the batter into the prepared sheet pan and smooth the top. Bake for 15 to 20 minutes or until a toothpick inserted into the center of the cake comes out clean. Allow cake to cool before glazing.

FOR THE GLAZE

1. In a large bowl, whisk together the powdered sugar, lemon juice, and lemon zest until completely smooth. 
2. Adjust consistency by adding more lemon juice if the glaze is too thick or more powdered sugar if it's too thin. 
3. Immediately pour the prepared glaze over the cooled cake and spread evenly.
4. If desired, garnish with lemon slices.
5. Chill (uncovered) for at least 30 minutes to allow the glaze to set before slicing. Cover tightly and refrigerate any leftovers.