In a medium bowl, sift together the flour, baking soda, baking powder, and salt. Whisk and set aside.
In the bowl of your mixer, beat the butter with the sugar until light and creamy. Scrape the bottom and sides of the bowl, beat again for approximately 30 seconds.
Add eggs one at a time, beating after each addition. Add the lemon zest, lemon juice and the vanilla extract.
With mixer running on low speed, add the flour mixture alternately with the sour cream, beginning and ending with the flour mixture. Approximately, ⅓ of the flour mixture, then add ½ the sour cream, add ⅓ of the flour, add the remainder of the sour cream, and then the rest of the flour.
Pour the batter into the prepared loaf pan and bake the loaf for 45 to 55 min. With a toothpick or a cake tester, check to see if the loaf is done at 45 min, if the toothpick comes out clean or with just a couple of crumbs the loaf is done, if not, check again in 5 minutes. Mine took 50 minutes to bake.
Place the loaf on a rack to cool for 15 minutes before removing the loaf from pan. Remove loaf and let cool until cake is slightly warm. Pour lemon glaze on loaf.
In a medium bowl, combine the confectioners sugar with lemon juice and cream or milk, whisk until smooth and pour onto the loaf while still slightly warm. Let glaze set for a few minutes before slicing and serving.