Question

How do you add lemon flavor to a cake?

Answer 1

add lemon extract too (we're trying to get as much flavour as possible into the cake!)
...
here are a couple of ideas:

1. add some limoncello to the batter.
2. after baking and initial cooling: apply a lemon sugar syrup. use a skewer to make holes in the cake. pour over the lemon syrup.
3. use lemon curd as a topping.