Fill the bottom pot of your double boiler with 1-2 inches of water. (Or use the DIY double boiler method listed in the notes.) Place on high heat. Once the water begins to boil, reduce to low heat to keep the water at a simmer. Place egg yolks, egg, granulated sugar, lemon zest, lemon juice, and salt into the top pot of your double boiler. Using a silicone whisk (avoid metal because it leaves an aftertaste), whisk until completely blended and then continue to whisk as the curd cooks. Whisk and cook until the mixture becomes thick and is the consistency of hollandaise sauce or a really thick soup, about 10 minutes or when an instant read thermometer reaches 160°F (71°C). If curd isn’t thickening, turn up the heat and constantly whisk. Remove pan from heat. Cut the butter into 6 separate pieces and then whisk into the curd until butter has melted and combined. Pour curd into a jar or bowl and place a piece of plastic wrap directly on top so it is touching the top of the curd. This prevents a skin from forming on top. The curd will continue to thicken as it cools. Place in refrigerator to speed up cooling. Once cool, the plastic wrap can be removed. Refrigerate the curd for up to about 10 days or for longer storage, you can freeze the cooled curd for up to 3-6 months. Thaw in the refrigerator overnight before enjoying. Makes 1 heaping cup.

Preheat oven to 350°F (177°C). Grease three 6-inch round cake pans, line with parchment paper rounds, then grease the parchment paper. Parchment paper helps the cakes seamlessly release from the pans. (If it’s helpful, see this parchment paper rounds for cakes video & post.)

Whisk the flour, baking powder, and salt together in a medium bowl. Set aside. Using a handheld or stand mixer fitted with a paddle or whisk attachment, beat the butter and sugar together on medium-high speed until combined, about 3 minutes. (Here’s a helpful tutorial if you need guidance on how to cream butter and sugar.) Scrape down the sides and up the bottom of the bowl with a silicone spatula and then add the citrus zest. Beat on medium-high speed until combined and creamy, about 2 minutes. Add the eggs and vanilla extract. Beat on medium-high speed until combined. Scrape down the sides and up the bottom of the bowl and beat again as needed to combine. Add half of the flour mixture (just eyeball it), half of the milk, and half of the citrus juice. Beat on low speed until mostly combined, and then add the remaining flour mixture, milk, and citrus juice. Beat on low speed until combined. Do not over-mix. You may need to whisk it all by hand to make sure there are no large lumps at the bottom of the bowl. The batter will be slightly thick with some small lumps. You will have between 3.5 – 4 cups of batter.

Divide and pour batter evenly into cake pans. If batter appears to have bubbles, give the pans a light tap on the counter to pop them. Bake cakes for 18-21 minutes or until baked through. To test for doneness, insert a toothpick into the center of the cake. If it comes out clean, it’s done.

Allow cakes to cool completely in the pans set on a wire rack for 30 minutes. Remove cakes from the pans and set them on a wire rack to cool completely. The cakes must be completely cool before frosting and assembling.

In a large bowl using a hand-held mixer or stand mixer fitted with a whisk or paddle attachment, beat the cream cheese on medium-high speed until creamy, about 1 minute. Scrape down the sides and up the bottom of the bowl and beat again as needed until creamy. Add the confectioners’ sugar and vanilla extract, and then beat on medium speed until combined and completely smooth (absolutely no lumps), at least 2 full minutes. Scrape down the sides and up the bottom of the bowl and beat again as needed to smooth out. Switch to a whisk attachment (if you haven’t already been using it). Turn the mixer to low speed and with the mixer running, carefully pour in the cream in a slow and steady stream. After all of the cream has been added, turn the mixer up to high speed and whip until thick and stiff peaks form, about 1-2 minutes. Do not walk away during this time and do not be concerned if your frosting takes longer to whip. You’re looking for a thick, airy consistency with stiff peaks. If your frosting appears soupy now or at any point you are working with it, it needs more whipping to introduce more air. If your frosting appears chunky or curdled, it’s over-whipped. To fix, stir 1 Tablespoon of heavy cream into the frosting by hand to smooth out again. You will have about 3.5 cups of frosting.

Spoon 1 cup of frosting (about 240ml) into a separate bowl. Stir in 3 heaping Tablespoons of cooled lemon curd. This will be your filling for the cake. Enjoy remaining lemon curd drizzled on the cake slices or as a topping on other baked goods.

First, make sure you have enough room for the cake inside your refrigerator because it must chill at the end of this step and briefly in the next step as well. If the cake layers aren’t flat on top, carefully and slowly level them off using a large serrated knife. Discard (or crumble over ice cream!). Place 1 cake layer on your cake stand, cake turntable, or serving plate. Evenly cover the top with 1/2 of the lemon curd frosting. Top with 2nd cake layer and evenly cover the top with remaining lemon curd frosting (if you have extras, just use it on the exterior of the cake). Top with the third cake layer. Spread a very thin layer of regular whipped frosting on top and all around the sides of the cake to create a crumb coat. A bench scraper and small icing spatula are handy for this. Refrigerate uncovered for 30 minutes.

Add remaining frosting on chilled crumb-coated cake using a small icing spatula or a larger flat icing spatula. Use a bench scraper, if desired, to smooth out the sides. Refrigerate the decorated cake uncovered for at least 30 minutes to help set the frosting. After that, if you used a cake turntable, you can carefully transfer the cake to a cake stand or serving plate using a couple flat spatulas.

After 30 minutes in the refrigerator, the decorated cake is fine to slice and serve or sit out at room temperature for a few hours. Cover leftover cake tightly and store in the refrigerator for 5 days.