Preheat oven to 350°F. Spray a 9x5 loaf pan with non-stick cooking spray and set aside until ready to use.
Combine flour, baking powder, salt, and one tablespoon of lemon zest in a small bowl. Set the bowl aside until ready to add to the batter.
Cream the butter in a large bowl for about two minutes until light and fluffy. Then, add the granulated sugar and beat for 4-6 minutes on medium-high speed until light and fluffy. Scrape down the sides of the bowl.
Next, add the eggs, one at a time, beating well after each addition. Scrape down the sides of the bowl. Then, beat in vanilla extract and fresh lemon juice. Scrape down the sides of the bowl.
Next, beat in one-third of the flour mixture, until just combined. Scrape the sides of the bowl. Add half of the buttermilk, beat until just combined. Scrape the sides of the bowl. Then, add another third of the flour, the remaining buttermilk, then the remaining third of flour, beating until just combined and scraping the sides of the bowl after each addition.
Use a large ice cream scoop to transfer the batter into the prepared pan. Bake in a 350°F oven for 45-55 minutes, until the top is golden brown and a toothpick inserted comes out mostly clean.
Remove the cake from the oven and let it cool for 15 minutes in the pan.