Preheat the oven to 350F. Grease two 8-inch round cake pans and line with parchment paper.
In a medium mixing bowl, whisk together the flour, baking powder, baking soda, and salt.
In a large mixing bowl or the bowl of a stand mixer fitted with the paddle attachment. Beat the butter on medium speed until creamy. Add the sugar and lemon zest and beat until light and fluffy, about 5 minutes. Add the vanilla then eggs one at a time, scrape down the bowl between additions, and beat until well combined and fluffy.
Stir the buttermilk and lemon juice together.
With the mixer on low speed, add a third of the flour mixture followed by half of the milk mixture. Continue, alternating between the flour and milk, mixing just until combined. Stop and scrape down the bowl occasionally. Divide the batter among the prepared cake pans.
Bake for 35 to 40 minutes or until the center of the cakes are springy to the touch and the sides are just starting to pull away from the pan. Let the cakes cool in the pan for 15 minutes then invert and cool completely on a wire rack.
For the frosting:
In a large mixing bowl or the bowl of a stand mixer fitted with the paddle attachment, beat the butter and cream cheese together on medium speed until creamy and well combined. Add the lemon zest and beat until light and fluffy, about 3 minutes.
With the mixer on low speed, gradually add the confectioners’ sugar alternating with a little bit of the lemon juice. Stop occasionally and scrape down the bowl. Beat in the vanilla. Once combined, increase the speed to medium-low and beat until smooth and fluffy, about 1 minute.
For the Assembly:
Remove the parchment paper from the cake layers. Place one layer on a cake stand or serving plate. Top with 1 cup of frosting, spreading smoothly out to the edges. Top with the second cake layer and spread the remaining frosting all over the outside of the cake. Decorate with thin lemon slices or edible flowers, if desired.
Video
Notes
Measure your flour correctly! Adding too much flour to the recipe is the most common mistake that will yield a dry and dense lemon cake. The best and easiest way to measure flour is by using a scale. If you don’t have one, fluff the flour with a spoon, sprinkle it into your measuring cup, and use a knife to level it off. If you scoop the flour straight from the bag, you overpack the measuring cup.
If the tops of your cake layers are domed, use a serrated knife to cut off the top so you can stack them evenly. Alternatively, if you’re worried about doming, use cake strips to help your cake layers come out evenly. Cake strips work by keeping the outside edge of the pan cooler to ensure that the entire cake rises at the same rate, preventing a dome from forming in the middle. If you don’t want to buy cake strips, I have a post on how to DIY cake strips.
Any ingredients that you keep in the fridge, take out ahead of time to bring them to room temperature, so they mix evenly into the batter.
Be gentle when handling the layers during assembly, as the cake is very tender.
When zesting the lemon, make sure only to zest the yellow parts. The white layer underneath is bitter.
To get more juice from the lemons, roll them under your hand on the countertop to loosen the juices.