I'm making a cake that requires vanilla extract in the icing. I only have enough of vanilla extract for my cake. Is it ok to use lemon extract in the icing instead? Or will it be too acid like to use?
It depends. What kind of cake are you making? It may be easier to switch an ingredient in the cake and use the vanilla in the frosting. Or, if you don't want a lemony frosting for your cake, you may be able to substitute in some alcohol or another flavoring, live a reduced maple syrup.
I'm making a caramel apple pound cake.... And at the last part, are you referring to maple syrup extract?
If you have maple extract, go ahead and use that in your frosting instead of the lemon. If you do not have maple extract, try boiling down maple syrup (4 tablespoons to 1 tablespoon). You want to concentrate the flavor. You can also add brandy or bourbon, which would go very nicely with caramel apple cake.
Alternately, if you want the frosting to be vanilla, you can use your extract for the frosting and substitute cardamon for the vanilla in the cake. I have done this before with apple cake and with oatmeal cookies. It is delicious and it gives a vanilla smoothness with a hint of citrus. Either solution should work. Good luck!
Lemon extract or orange extract, or some zest of either one does wonder to a cream cheese icing or cheesecake.
I'm assuming it may be too late, but I would not sub for lemon extract with the apple cake. Either add in booze as suggested below or maple syrup (adjust for sweetening), or just leave it out completely.