Preheat your oven to 350°F (175°C). Grease and flour a 9x5-inch loaf pan.
In a large bowl, cream the butter and sugar together until light and fluffy.
Add the eggs one at a time, beating well after each addition.
Mix in the lemon zest.
In another bowl, whisk together the flour, baking powder, baking soda, and salt.
Alternate adding the dry ingredients and buttermilk to the butter mixture, starting and ending with the dry ingredients.
Stir in the lemon juice and vanilla extract until just combined.
Pour the batter into the prepared loaf pan and smooth the top.
Bake for 45-55 minutes or until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.