Pre-heat oven to 325°F. Lightly grease an 8" x 4" loaf pan and line it with a piece of parchment paper, so that the paper covers the bottom of the pan and extends up the long sides about an inch past the top.
Beat together butter and sugar until pale and fluffy (about 3 minutes).
Add the eggs on at a time, beating well after each addition.
Add the lemon zest, lemon juice, and vanilla. Beat until combined.
In a separate bowl, whisk together the flour, salt, baking powder and baking soda.
Alternate adding the flour mixture and the sour cream to the butter mixture, starting and ending with the flour. (Add 1/3 flour, 1/2 sour cream, 1/3 flour, 1/2 sour cream, 1/3 flour). Mix between each addition.
Transfer batter to prepared loaf pan and baked for 55-60 minutes, or until a tester comes out clean. Let cool in pan for 15 minutes before transferring to a wire rack to cool completely.