Step 1

Preheat the oven to 350° and grease a 6” round cake pan.

Step 2

In a medium bowl, beat together with an electric mixer the butter, sugar, and lemon zest. Beat very well, about 1-2 minutes.

Step 3

Add the egg and beat until well combined, about 15 seconds.

Step 4

In a small bowl, whisk together the flour, salt and baking soda. Add half of this to the batter and beat lightly.

Step 5

Stir in half of the buttermilk and continue beating. Add the remaining dry ingredients and beat, then stir in the remaining buttermilk and 1 tablespoon of lemon juice.

Step 6

Scrap the batter into the pan, smoothing the top and bake for 37-39 minutes, until a skewer inserted comes out clean.

Step 7

Let cool on a wire rack in the pan. Carefully remove the cake from the pan once it has cooled and set aside.

Step 8

Meanwhile, make the lemon curd: In a microwave-safe bowl, whisk together all of the ingredients very well. Microwave on HIGH for 1 minute. Stop, stir, and then microwave another minute. Stir the lemon curd after 2 minutes, and then place it back in the microwave for a final 30 seconds. After 2 minutes and 30 seconds, begin testing the lemon curd by quickly dipping a spoon into it, and running your finger through it. If the line holds, the lemon curd is done. If the curd runs and fills the line you just made, try another 30 seconds in the microwave and test again. The curd will thicken considerably as it cools.

Step 9

Strain the curd through a fine-mesh strainer into a small bowl, and set aside.

Step 10

When ready to assemble, slice the cake in half horizontally. Do this on a flat surface and cut slowly to ensure both cake layers are even. Flip the cake layers over so that the bottom is now the top so that you have a flat surface to frost the cake.

Step 11

Place one half of the cake on a cake stand or desired serving plate. Top with the lemon curd. Spread it almost to the edge.

Step 12

Top with the remaining cake layer. In a medium bowl, beat the heavy cream and powdered sugar together until whipped and slightly stiff—do not over-beat. Frost the cake with this mixture. Slice and serve.

Step 13

If you're not serving immediately, refrigerate the cake, but then let it sit at room temp for about 15 minutes before serving.