For the cake: Preheat oven to 350 degrees and grease 2 (9 inch) round baking pans. In a medium mixing bowl stir together flour, baking powder, and salt. Set aside.
In a medium saucepan heat butter and milk over low heat just until mixture is hot and butter is melted. Remove from heat.
Meanwhile, In a large mixing bowl with an electric mixer on medium speed beat eggs, sugar, and vanilla until lightened in color and thickened. On low speed gradually add flour mixture and beat until blended. Slowley add hot milk mixture and beat until combined.
Divide batter evenly between baking pans. Bake until toothpick inseted into center comes out clean, about 40 minutes. Cool cakes in pans for 10 minutes then invert cakes onto cooling racks to cool completely.
For the frosting: In a medium mixing bowl with an electric mixer on medium speed cream butter and cream cheese until smooth. On low speed Gradually add powdered sugar. Add vanilla and lemon zest and beat until smooth.
To assemble: Carefully split each cooled cake into half horizionally. Layer each cake layer with lemon curd. Frost the cake with the frosting. Keep cake in the fridge.