Preheat the oven to 350F. Beat butter and sugar until combined. Add eggs, vanilla bean paste and lemon curd, continue beating until fluffy. Add all purpose flour and also buttermilk. Continue whisking for 1 more minute.
Add lemon zest and stir. Transfer the dough to a 7-inch round shape. Cover with foil and place in the oven. After half an hour, remove the foil and bake for another 15-20 minutes (45-50 minutes in total).
Let the finished lemon cake cool for 20-30 minutes (or more if necessary). Itis better to apply frosting on a cooled cake. Beat cream cheese, icing sugar and lemon curd until fluffy. Transfer the icing to a piping bag fitted with a star tip.
Apply frosting on top of the cake. You can also use a spatula to spread the frosting