Step 1

Preheat oven to 325°F.

Step 2

Prep the pan: Butter the bottom of a loaf pan. Cut a piece of parchment paper so it covers the bottom of the pan and goes up the long sides of the pan like a sling. The short sides shouldn’t be covered. Leave enough parchment hanging over each side so that you can easily lift the loaf out of the pan.

Step 3

Whisk dry ingredients: Whisk together the flour, salt, and baking soda. Set aside.

Step 4

Begin making the batter: In the bowl of a stand mixer fitted with a paddle attachment, beat together the sugar, butter, and lemon zest on medium to medium high for 8 minutes. Stop occasionally to scrape down the bowl.Add the sour cream and beat for one more minute, scraping down the sides of the bowl halfway through. One at a time, add the eggs and egg yolk, scraping down the bowl between additions.Add the lemon juice and beat for 1 more minute scrape down the sides of the bowl halfway through, and once more before adding the flour.

Step 5

Add the flour to the batter: Set the stand mixer to stir (or the lowest setting) and add the flour mixture. Stir for about 1 minute or until the flour is just incorporated. Shut off the mixer and remove the bowl.Use a spatula to scrape the sides and bottom of the bowl, and finish folding the ingredients together. The batter will be thick and velvety.

Step 6

Bake the pound cake: Scrape the batter into the prepared loaf pan. Smooth the top with a spatula.Bake for 1 hour and 35 minutes, or until a skewer inserted into the center of the cake comes out clean.

Step 7

While the lemon cake bakes, make the lemon soaking syrup: In a small saucepan set over medium high heat, combine sugar, lemon juice, and water. Stir occasionally and bring to a low boil.The syrup is ready when it looks transparent and is no longer cloudy. This should take about 5 minutes. Let the syrup cool.

Step 8

Soak the cake with syrup:  Once the cake has finished baking, remove it from the oven. It will have a slight crack down the center. That’s ok. Let the cake cool in the pan for 10 minutes.With the cake still in the pan, pour half of the lemon syrup over the entire cake. Let it soak in. Then pour the remaining syrup over the cake. Let it continue cooling in the pan for another 15 minutes.Run a knife along the ends to help release the cake. Use the parchment sling to lift the cake out of the pan, and set it on a baking rack to let it cool completely.

Step 9

While the cake cools, make the icing: In a medium microwave-safe bowl, melt the butter in the microwave for 10 to 20 seconds. Make sure you cover it so you don’t end up with splattered butter everywhere.Add the powdered sugar. Whisk together while adding the lemon juice one tablespoon at a time.

Step 10

Frost the cake: Once the cake is completely cool, pour the icing over the lemon pound cake. Gently spread the icing so it completely covers the top. It should be white and thick. Slice and serve.