Cooking parve food in a meaty oven/pot

I would like to bake rolls in my meaty oven and then serve them for a milky meal. Is there a problem of nat bar nat?

Thank you for your question

Nat Bar Nat explained:

In halacha, even if a utensil is clean, it can still be called meaty or milky. The reason is that when one uses it to cook, the taste that was absorbed inside the dish will be extracted through cooking, and will then give a meaty taste to the parve food that is being cooked inside the pot, the dish will then be considered meaty. (Generally, the food in the pot does not have sixty times the volume (shishim) against the surface of the pot it is being cooked in).

This concept is called 'nat bar nat,' literally 'taste after taste.' This means the original taste of the meat entered the pot, and then when cooking again, it imparts taste a second time to the new dish that is cooking in the pot. Since this is only considered a 'second-degree taste,' there are certain leniencies, as will be explained.

Of course, there is a difference in halacha if the second cooking occurs within twenty-four hours of the original cooking. We call this 'ben yomo,' or whether it was after twenty-four hours, in which case we are more lenient. This is called 'eino ben yomo’.

Cooking parve food in a pot:

If it was used within twenty-four hours—'Ben Yomo':

Sephardic custom: one may eat it with meat.

Ashkenazi custom: one may not mix it with meat; however, if it accidentally got mixed into meat, it is then permitted to eat.

According to all customs, The above halacha applies only if one has already started cooking and then realized or decides to later mix it into meaty food. However, one should not intentionally cook in a milky pot in order to later mix the food into meaty food, or vice versa.

If the pot was not used within twenty-four hours—'eino ben yomo':

Sephardi custom: It is permitted to intentionally cook parve food in this milky pot to mix it later into meaty food.

Ashkenazi custom: One should not start to cook pareve food in the pot with the intention to later mix it into meaty food; however, if it was already cooked in the pot, one may le’chatchilah mix it into meaty food.

According to the Ashkenazi minhag, if one does not have a pareve or meaty pot at home, one may le’chatchilah cook in the milky pot which wasn’t used within twenty-four hours. One doesn’t even need to ask a neighbor to borrow a meaty pot.

Cooking Parve food in an oven:

So, with regard to the oven that you mentioned, it was a meaty oven, and you want to bake bread within twenty-four hours of the original cooking.

The Halacha is, that if you use a pareve tray, or even if you used a meaty oven tray but you place the parve food either on baking paper and make sure that it seals the food and prevents contact with the meaty tray, you can still consider the bread baked in the oven as parve. Therefore, one may eat the bread even together with milk. This rule applies even if the oven is ‘ben yomo’ (used within the last twenty-four hour

The reason for this is, that since the tray is parve and only steam from the food rises without returning back to the food after touching the sides of the oven, we could even say that the steam gets burnt upon contacting the walls of the oven. That is why the halacha of the oven differs from that of the pot. Since when cooking in a pot, the food touches the surface of the pot, and therefore, the food will not be considered pareve as explained above.

All the above halachot of 'nat bar nat,' which was explained above, do not apply to spicy foods or non-kosher food that was originally cooked in the pot. In these instances, the halacha would be completely different.

Wishing you much success.

Shulcha Aruch YD Siman 95

Pesakim Ve'horaot page 78