I can't seem to find what is wrong with this sentence. my teacher told me it was a "tense problem"?

I can see what your teacher is saying, but, to be honest, it's a bit pedantic. By saying "ever since that day" you are saying that the activity is still ongoing, however you then say "I would go over" suggesting the activity has ceased. To correct it change the sentence to "Ever since that day, during the holidays i go over and cook them a lovely meal and bring over baked goods." if you are still doing it, or "For [insert time period here] after that, during the holidays i would go over and cook them a lovely meal and bring over baked goods" if the activity has stopped. Good luck.