Preheat oven to 325°
Line a 9" round baking pan with parchment paper or lightly spray with cooking spray.
Mix together the flour, baking powder, baking soda, salt and lemon zest and set aside.
In a small measuring cup, combine lemon juice, buttermilk and vanilla.
With an electric mixer, cream the butter and sugar for about 5 minutes until light and fluffy. Scrape the sides with spatula.
With the mixer on medium speed, add the eggs, 1 at a time,beating well between each addition. I like to turn off the mixer while I'm adding the eggs in case a bit of egg shell gets in there -- easier to fish it out with the machine off!
Add the flour and buttermilk mixtures alternately to the batter, beginning and ending with the flour. Scrap the sides with spatula as needed.
Pour batter into pan, smooth the top, and bake for 30 minutes til a toothpick comes out clean. Let cool in pan for about 15 minutes then remove to a wire rack to cool completely before drizzling with Lemon Glaze.