Preheat oven to 350 degrees. Butter cake pans, dust with flour, tap out excess. Sift flour, baking powder, and salt into a large bowl.
Cream butter, sugar, and lemon zest with a mixer until pale and fluffy. Add eggs, 1 at a time, mixing well after each. Beat in vanilla. Reduce speed to low; add flour mixture in 3 additions, alternating with buttermilk and lemon juice.
Pour batter into prepared pans. Bake cakes until golden brown and testers inserted in centers come out clean. Let cool on a wire rack for 15 minutes. Immediately run a knife around edges of pans to loosen cakes; invert cakes. Let cool.
Cakes will keep, covered and refrigerated, for up to 3 days.
I ultimately chose to make this for my daughter's first birthday party. It's not for beginners but wow was it a hit! It got rave reviews. The yellow color was appropriate, but it would have also looked cute with some pink coloring in the frosting or in the cake itself. The curd piped nicely-- well enough for a message and some basic dots and lines to pretty it up. Tasted great and the kids really liked it; I was afraid it might be too tart but I'm glad I took the chance on this cake.
should roughly fill 2 9" rounds
How do I adapt this for a regular birthday cake? There's no mention here of volume, or even how many pans.