This lemon frosting gets its bright, fruity flavor from real lemon curd! It's got a silky smooth texture and pipes beautifully, making it the perfect choice for topping both cakes and cupcakes.Don't forget to watch the how-to video!Recipe makes enough frosting to thoroughly cover one 9x13” cake, a 2-layer 8” or 9” cake, 24 cupcakes (modestly) or 12 cupcakes (generously). This recipe will also fully cover my (3 layer) lemon blueberry cake as the layers are thin, but if you like extra frosting or want to do decorative swirls I recommend increasing the recipe by 50%.
In a small, non-reactive saucepan (see note), whisk together egg yolks, lemon juice, sugar, and salt.
2 large egg yolks, ⅓ cup lemon juice, 2 Tablespoons granulated sugar, ¼ teaspoon table salt
Add butter and cook over medium-low heat, whisking constantly until mixture is thickened (the whisk should leave trails through the curd and it should be able to coat the back of a spoon, see video or photos in post for visual if desired).
4 Tablespoons unsalted butter
Remove from heat and pour through a fine mesh strainer into a heatproof bowl. Allow to cool completely before proceeding (you can transfer to the refrigerator to cool faster).
Using an electric hand mixer or stand mixer, beat 1 cup softened butter until light and fluffy (high speed about 30-60 seconds). Gradually add powdered sugar until completely combined.
1 cup unsalted butter, 3 cups powdered sugar
Drizzle in cooled lemon curd and stir until completely combined. Be sure to scrape the sides and bottom of the bowl to ensure ingredients are well-combined. Note: if frosting is too thin you can add additional powdered sugar, up to 1 cup/125g.
Spread or pipe over cake or cupcakes.
You must use a non-reactive pan when making lemon curd. Acceptable materials include stainless steel, glass, enameled cast iron. Avoid using aluminum, copper, or iron (such as non-enameled cast iron) pans, which can react with the lemon and cause a metallic taste.
Storing/Making in Advance
The lemon curd can be made up to a day in advance, simply store in the refrigerator in an airtight container until ready to use (you do not need to return to room temperature before using). The assembled frosting may be prepared and stored in an airtight container in the refrigerator for 2-3 days before using, you will need to let the frosting return to near room temperature and stir until smooth before using. Once used to decorate a cake/cupcake, the frosting may sit at room temperature for several hours but for best results I recommend refrigerating.