Preheat oven to 325°F. Lightly spray two 9x5" loaf pans and line each with parchment paper. Set aside.
Add butter to a large mixing bowl and beat on medium with a hand mixer until light and fluffy. Add sugar and beat again until fluffy and combined.
Add eggs and beat until combined. Add sour cream, vanilla, lemon juice, lemon zest and milk, then beat until combined.
In a separate mixing bowl, add flour, baking powder and salt, whisking until well mixed.
Add flour mixture to batter and stir with a rubber spatula until JUST combined and no flour streaks remain.
Divide batter evenly among the two prepared loaf pans, using the spatula to smooth the batter into an even layer.
Bake in preheated oven for 40-50 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs on it.
Remove from oven and let cool.
While cake is cooling, in a small mixing bowl, add all sweet lemon glaze ingredients (powdered sugar, lemon juice, milk and the optional lemon zest).
Whisk well until smooth. Once cake has cooled, remove it from the pan and pour the glaze over the top of the cake.