My girlfriend got mad at me because I told her the truth about her baking skills. Is this fair?

You could have delivered the truth  without being such an  a** about it.   Grow up. 

damn what a waste of nice food

You hurt her feelings. Of course it isn't fair. How would you feel if she told you, you can't do sh!t in bed?

No it was not fair. She baked you a cherry pie out of wanting to make you happy.  You did not have to be a dyck to prove a point.  And who cares if you are blunt or not.  There is a thing called being a dyck and someone that has tact.  And you my dear need to learn tact.  Not everyone thinks its "cute" to be blunt. 

Apologize to her and tell her next time she wants to do something as nice as she did, you can both bake one together... and then.. see how your cooking skills are.

Frankly.. I would not have even come back to the house... ever.  And its not about the pie.. its about how you treat someone.

Listen.. a person may never remember what you say.. but they will ALWAYS remember how you make them FEEL.

Here a little advice whatever she does or asks you about anything she did just for you, giving a negative response think twice as she takes it personally that is what you are saying is she doesn't know how to please you and it's the worst thing you can say to a woman in a relationship.

Yeah she sounds a bit nutballs. Throwing a pie against the wall? (that’s actually domestic violence). That’s some red flag sh*t right there. Have her clean the wall then kick her to the curb. Her insecurities will only lead to more freak show drama. 

Other people commenting are saying you’re the one that messed up. Maybe your delivery could have been handled differently. However, her reaction was way beyond normal. 

It's often not what you say but how you say it. 

If you were quoting yourself verbatim then I can see why she would think you are rude and ungrateful. 

The delivery was bad , apologize to her and tell her that the cherry pie was bad but i should have been more careful with how i said it. 

Geez...Is that what you said?  "Can't bake for ****"?  If you're going to criticize your girlfriend for something nice she did for you--which is not very kind--at least do it in as soft words as possible.  Also, maybe choose some better time than that to criticize her baking skills.

Not caring about hurting people's feelings is not an attractive quality.  And I'm certain that's not what she meant by straightforward.

My mother was an award winning home baker. I wish I had her cherry pie recipe. It was handed down from the 1800s. It was the best, but mother is gone now, and perhaps my sister has it. It won 1st prize at a 'cherry festival' pie baking contest.