Preheat your oven to 325°F (165°C). Grease and flour a 9x5 inch loaf pan, or line it with parchment paper.
In the bowl of an electric mixer or stand mixer fitted with the paddle attachment, cream together the softened butter and granulated sugar until light and fluffy, about 3-4 minutes.
Beat in the eggs, one at a time, making sure each one is fully incorporated before adding the next. Add the lemon zest and vanilla extract, mixing until well combined.
In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing just until combined.
Add the sour cream and lemon juice to the batter, mixing until fully incorporated. Be careful not to overmix.
Pour the batter into the prepared loaf pan, smoothing the top with a rubber spatula.
Bake for 1 hour and 30 minutes to 1 hour and 45 minutes, or until a toothpick inserted into the center of the cake comes out clean.
Allow the cake to cool in the pan for 10-15 minutes, then carefully remove it from the pan and transfer it to a wire cooling rack to cool completely.
While the cake is cooling, prepare the lemon glaze. In a small bowl, whisk together the powdered sugar and lemon juice until smooth.
Once the cake is completely cooled, drizzle the glaze over the top, allowing it to drip down the sides.