All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Since the husband knew in advance about that and since it is his wife's only defect and he did not see any other defect either in her morals or religiousness and that she further fulfills his rights, he should not divorce her. In a Hadeeth, the Prophet, sallallaahu ‘alayhi wa sallam, said: “Among lawful things, divorce is the most hateful to Allaah.” [Abu Daawood and Ibn Maajah; Al-Haakim: Saheeh]
A husband should know that his wife's ignorance about cooking does not necessitate divorce. It is possible that she learns cooking from his mother, sister, or any other woman, for one knows by means of learning. So, keep your wife, fear Allaah and do not divorce her for this simple matter which could be rectified.
Allaah Knows best.