Preheat the oven to 350°F/180°c. Brush a 12 cup bundt pan with butter, or spray with a non-stick cooking spray. Dust with flour and set aside. Add the softened butter and granulated sugar to the bowl of a stand mixer.
Beat on a medium-high speed using a flat beater attachment for 2 minutes, or until pale and creamy.
Add the eggs, one at a time, beating on a medium speed until well combined between each addition. Add the sour cream, lemon juice, lemon zest and vanilla extract, and beat on a medium speed until well combined, scraping the sides of the bowl as necessary.
Add half of the flour, along with all of the baking powder and salt. Beat on a low speed until just combined. Add the milk and beat once again on a low speed until combined. Finally, add the remaining flour and beat until just combined.
Pour the batter into the prepared bundt pan, and tap the pan a few times to remove any bubbles. Transfer to the preheated oven and bake for 45-50 minutes, or until cooked through.
Allow to cool in the pan for 10 minutes, before turning onto a cooling rack to cool completely.
To make the lemon glaze, whisk together the powdered sugar, lemon juice and melted butter in a medium mixing bowl, adding extra lemon juice if necessary.
Drizzle over the cooled cake before serving.