Preheat oven to 350°F / 175°C. Line a 10-in x 5-in loaf pan with parchment paper.
In a medium bowl, whisk together the flour, lemon zest, baking powder, and salt. Set aside.
In a small cup, mix together the sour cream, lemon juice and vanilla. Set aside.
Place the butter and sugar in a large mixing bowl, and cream together on medium speed until very pale and fluffy. Stop and scrap down the bowl as necessary. It should take about 5 minutes.
Slowly add in the eggs, one at a time. Beat each egg into the butter mixture before adding the next one.
Alternate and mix in the dry and wet ingredients, starting and finishing with the dry ingredients. In other words: - Add in ⅓ of the flour mixture and beat until just combined. - Pour in ½ of the sour cream mixture and beat until just combined. - Add in ½ of the remaining flour mixture and beat until just combined. - Pour in the remaining sour cream mixture and beat until just combined.- Add in the remaining flour mixture and beat until just combined.
Pour the batter into the prepared loaf pan. Smooth the top with a spatula so the batter is even. Bake for 55-65 minutes, or until a toothpick inserted in the middle of the cake comes out with just a few crumbs.
Remove from oven and allow the lemon pound cake to cool in the pan on a cooling rack for at least 20 minutes. You can allow the pound cake to finish cooling in the loaf pan completely. Or to speed it up, transfer the lemon pound cake to the cooling rack to completely cool.
You can enjoy this easy homemade pound cake the day it is baked, but for the best flavor, allow it to sit overnight.