Prepare lemon curd ahead, as directed. Can be prepared days or weeks ahead of time. Keep chilled until ready to use.
Preheat oven to 350°F. Grease and flour 3: 8-inch round pans, discarding extra flour. Optionally, parchment paper may be added to the bottom of each pan, but is not necessary. Set aside.
In a large bowl or stand mixer, cream together butter and sugar, beating until light and fluffy. Mix in eggs one at a time, followed by lemon zest, lemon juice and vanilla extract. Mix until just combined. With mixer on low, add salt, baking powder and baking soda. Finally, alternate additions of flour and sour cream, mixing until fully combined and no streaks remain. Divide between prepared baking pans. Use a small offset spatula to spread batter into an even layer. *(see note)
Bake cakes for 20-25 minutes or until a toothpick inserted comes out clean. Cool completely in pans, set on a wire rack. When cakes are cool, carefully run a knife or metal spatula around the edge of the cakes. Invert pans and wrap well in plastic. Store overnight in the refrigerator to firm up.
In a medium bowl, prepare lemon buttercream. Beat together butter and powdered sugar, followed by lemon juice. Mix until just combined. Transfer to a piping bag fit with a small round tip, or snip off the end, creating a 1/4-1/2-inch opening.
Place one cake layer on a cake turntable or cake stand. Pipe a border of frosting around the top edge. This will create a wall to hold the curd in. Add roughly 1/2-cup lemon curd to the center of the first cake layer. Spread out with a small offset spatula to the edge of the frosting. Place a second layer of cake on top, pipe an additional edge of frosting and fill with remaining lemon curd. Top off with remaining cake layer. Chill cake while preparing meringue frosting. If using a cake turntable, transfer cake to desired serving plate or cake stand prior to frosting with meringue.
In a large metal bowl, set over simmering water, whisk together egg whites, granulated sugar and cream of tartar. Continue whisking until frothy and egg whites are warm to the touch. Transfer bowl to a stand mixer, fit with a whisk attachment. Beat until stiff and glossy peaks form. Add vanilla in last 30 seconds. Meringue may be spread on the cake with an offset spatula or added to a large piping bag fit with a large flat piping tip. Start at the top or bottom of the cake, working your way in the opposite direction. Use an offset spatula or teaspoon to create patterns in the frosting. Lightly char with a handheld kitchen torch.
Slice and serve.
Store remaining cake covered in an airtight container for up to several days. For best results, press plastic wrap against exposed cake layers to retain freshness.
Notes
Serves roughly 10-14, yields 1: 3-layer 8-inch cake.*If fewer than three 8-inch pans are available, divide batter equally between clean bowls and prepared pan(s). Repeat preparation and baking process as directed.An original recipe from Baked by Rachel
Nutritional information is provided as a courtesy and is an estimate only. Nutrition information can vary for a variety of reasons. For the most accurate data, use your preferred nutrition calculator with the actual ingredients you used to make this recipe.
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