“Its fierce kiss will stay on your lips, possessive and faithful”
Metaphor / Personification
Images of jealousy and violence. The onion is compared to a jealous lover and the way their kiss at this point in the relationship would be a mixture of passion and punishment. Compassion to an onions smell: it clings stubbornly to our fingers when we cut it.
Word choice of ‘possessive,’ hints at obsessive love : this is turning into an unhealthy relationship.