If I bake a cake in a Pareve oven using clean utensils that are sometimes used for Fleishigs, is the cake considered completely Pareve?
No, it is not necessarily completely Pareve.
To make a cake Pareve, you have to put the cake in a disposable dish, Pareve dishes, or with a piece of aluminum between the cake and the Fleishig dish.
If you wish to bake it in a Fleishig or Milchig oven, and want to ensure that the cake remains Pareve, you have to make sure:
1) The oven should be clean.
2) Heat up the oven on high heat for about half an hour.
3) Put the cake in disposable dishes, Pareve dishes or a piece of aluminum between the cake and the Fleishig or Milchig dish.
Sources:
טעמים ומקורות: עיין שו”ע יו”ד צ”ה ס’ א-ב רמ”א ונו”כ שם. שם ס’ ק”ה ס”ז ברמ”א.
שו”ע אדה”ז תנ”א סי”ג, ס”ע, שליבון קל הרי הוא כהגעלה.
For more information see also the following articles:
here,
here,