To make the cake: Prepare the cake mix per the package instructions using the amounts of water, oil and eggs called for. Add 1 tablespoon fresh lemon zest. Bake in a greased 13 x 9 inch cake pan until a toothpick inserted into the center comes back clean.
Once baked, immediately poke holes all over the cake using the back of a wooden spoon or similar. Be generous.
To make the pudding: In a medium size mixing bowl using an electric mixer, whip together the pudding mix and milk until thickened but, still pourable.
Spread pudding over the cake gently pushing into the holes. Cool to room temperature. (This doesn't take long)
To make the frosting: In a medium size mixing bowl using an electric mixer, cream together cream cheese, powdered sugar, lemon juice and lemon extract.
Add the cream continuing to beat on medium-high speed until fluffy and fully combined and soft peaks form. Mix in 2 tablespoon lemon zest by hand.
Frost the top of the cake, garnishing with the remaining lemon zest and grated white chocolate.
Chill for 4 hours or overnight before serving. (May use additional whipped cream and lemon slices to decorate as pictured, if desired.)
Store leftovers chilled.