I love writing cute fluff, so you've come to the right address. There's different ways Characters show love, so it'll depend on the Character what may be cute for them. Some show physical contact, some will more easily show their love in words.
I mean, banter is always fun, but for my characters I think it's the moments where they are opening up to each other or the moments where they are doing something positive without thinking about it for the other person are cute moments.
For example, in one of my latest episodes Joey unconsciously stops teasing my MC so he won't drop his camera, because he knows that'll make him upset and later on in the story they start getting so comfortable that they start having more physical contact unconsciously, so hugging, grabbing each other's hand when they're exited, stuff like that.