Preheat oven to 325 F. (not convection bake). Spray an 8x4-inch loaf pan with baking spray and line with a piece of parchment paper that covers the bottom and long sides, with an inch or so extending past the top of the pan (these will be the "handles" to lift the loaf out of the pan).
In a large bowl with an electric mixer or in the bowl of a stand mixer fitted with a paddle attachment, cream the butter with the sugar at medium speed (about "4 or 5" on a KitchenAid mixer) until light coloured and fluffy. (Don't skimp on this process. It should cream about 3 minutes). Add the eggs one at a time and beat in well after each addition, scraping down the sides of the bowl, as needed. Beat in the lemon zest, lemon juice and vanilla.
In a separate bowl, whisk together well the flour, salt, baking soda and baking powder. With mixer on low, add the flour mixture to the butter mixture alternately with the sour cream, starting with 1/3 of the flour, 1/2 of the sour cream, 1/3 of the flour, last of the sour cream, then finally the last of the flour.
Scrape into prepared 8x4-inch loaf pan and level batter. Bake in preheated oven for 55-60 minutes, or until a tester inserted in the centre comes out clean.
Allow to cool in the pan for 15 minutes, then run a knife along the short ends and use the parchment paper edges to lift and remove from pan. Allow to cool on a cooling rack.
While loaf is still a little warm, prepare the glaze by stirring together all the glaze ingredients in a small bowl, adding enough lemon juice to make a pourable glaze. Place a baking tray under the cooling rack to catch any drips and spoon glaze slowly over top of loaf, allowing it to drip down the sides a bit. Cool completely, then slice and enjoy.
Be sure to read the “Ingredient and Cook's Notes" (above the recipe card!), where I share more detailedtips, variations and substitution suggestions for this recipe!