For gingerbread, preheat oven to 325 °F. Grease 2 8-inch round cake pans, line the bottoms with parchment, and grease and flour, shaking out excess.
Beat butter until light and fluffy. Add sugars and beat well again. Add eggs, one at a time, beating well after each addition. Continue beating on high speed for 2 minutes (this adds structure for a light cake). Reduce speed to medium and add molasses, ginger and lemon zest.
In a separate bowl, sift flour, baking soda, salt and spices. Add to butter mixture and stir just until incorporated. Stir in milk and lemon juice and scrape into prepared pans, tapping pans gently to remove large air bubbles. Bake for 50 to 60 minutes, testing by pressing center of cake – it should spring back when pressed. Allow cakes to cool 30 minutes in pan before inverting to cool completely on a rack.
For icing, beat cream cheese until fluffy. On low speed, beat in icing sugar, then increase speed and beat until smooth. Blend in lemon juice and zest.
To assemble, slice cake in half, spread 1/4 of the icing on one cake layer, top with second cake layer. Spread remaining icing over top, running a butter knife or off-set spatula in circles to create swirls. Chill until ready to serve, but remove from refrigerator 30 minutes before slicing.
Candied lemon slices for garnish
Preheat oven to 275 and line a baking tray with parchment. Dip lemon slices in syrup, shake and place on tray. Bake 40-50 minutes until shiny and slightly golden brown.
Store in an airtight container until ready to use.