In a large bowl or stand mixer, beat together butter and sugar until light and fluffy. Mix in one egg at a time, followed by vanilla. Mix in lemon curd
and optional zest, followed by salt, baking powder and baking soda. Alternate additions of flour and sour cream, mixing until just combined. Transfer batter to prepared baking pan. Use a small offset spatula to carefully spread out into an even layer. Generously sprinkle with crumb coating.