菜 own its own means ‘vegetable’ or ‘dish’, however, in modern time we also refer 菜 to ‘one’s type’ credit to the famous taiwanese presenter 吴宗宪Wú zōng xiàn who introduced this saying during one of his entertainment shows, where he jokingly said to the female presenter that she is not his type.
nǐ bú shì wǒ de cài
You are not my dish…which also has the meaning that you are not to my taste, I don’t like you.
On the other hand, if you want to say that some one is your type,
nǐ shì wǒ de cài
你是我的菜。 You are to my taste, I like you.
Note we sometimes also use it to people we like/don’t like, it does not only apply to romantic interest.
More over, 菜 can also apply to things, for example,
Zhè jiàn yī fú shì wǒ de cài
这件衣服是我的菜。 This piece of clothes is to my taste.
Zhè fù yǎn jìng bú shì wǒ de cài
这副眼镜不是我的菜。 This pair of glasses is not to my taste.
zhè ge fǎ xíng jué duì shì wǒ de cài.
这个发型绝对是我的菜。 This hair style is definitely to my taste.