¿Estás viniendo por/para lasaña?
I sometimes have a hard time when it comes to por - reason / para - purpose, I often get confused on which to use.
Would it be para since it is assumed you will "cenar/ comer/ almorzar" the lasaña?
English sentence: Are you coming for lasagna? (to come eat lasagna)
6 Answers
If you had to choose one for your example it would have to be para but actually I would suggest using neither por nor para.
Following verbs of motion I think using 'a' sounds more natural.
¿Vienes a mi casa a cenar?
O ¿vendras a mi casa a cenar?
Para if you are asking them to come and eat and por if you are asking them to come and pick it up.
No te entiendo muy bien: ¿Quieres que me voy a la tienda para comprarte un paquete de lasaña?
o , quieres una invitación para cenar conmigo?¡ Me encantaría cocinar la comida italiana como la lasaña, y te invito!

Katy, I agree with KiwiGirl, .... a cenar is much more natural because of the word combination. Para lasaña would never work in this case because this would indicate that the lasaña is benifitting from the person arriving. Por would indicate the reason, but it dosen´t work with comer.
If we use dinero, it would work: Vengo por el dinero .... I coming to collect.
Also in your senario, gerund of venir should not be used unless you are referring to the very moment that the guest in enroute.
Come on Katy:
you can do better... start exchanging, in English, different contexts....with what you know from Spanish.
I am sure you will come up with a way to clarify it yourself.
If you are still having problems, let me know.
vas a ir por betty?
Are you going to pick up betty?
ve al super a comprar lasana
go to the market and buy lasagna