On the topic of onions creation, Yaakov Avinu asked for maadanim- plural.
The Alter Rebbe explains that there are two types of Avodas Hashem that Hashem delights in, and they are reflected in the two types of delicacies :
Avodas hatzaddikim – where we go from strength to strength in kedusha – that’s reflected in naturally sweet delicacies – like fruit.
Avodas Baalei teshuva – when we fall into bad / darkness, but then we elevate it into kedusha through teshuva, so we turn the darkness into light and bitterness into sweetness.
This is reflected by delicacies that start off bitter, but through cooking etc become sweet, such as onions.