Best Answer - Chosen by the Asker
First of all, instead of sentences, they are called phrases, because they do not have a complete thought yet (like a doer of action and the action itself).
But "Chocolate and lemon cake" can be interpreted in three ways:
1. A chocolate (bar, candy, or any kind of chocolate) and a lemon cake
2. A chocolate cake and a lemon cake
3. A cake that tastes like chocolate and lemon together
That's why it sounds a little confusing as it is, and will depend on how it is used in a bigger context.
"Chocolate cake and lemon cake", well, seems to mean as it is already. :)
