abbreviations - Usage of Can't - I can't tell VS can't you tell

I was reading a poster recently which stated:

Babies love skin on skin – can't you tell?

And I realized that while this is perfectly grammatical, if I were to now replace can't with can not (which is the non-abbreviated form) it would no longer be so:

Babies love skin on skin – can not you tell?

I found this interesting because generally it would be fine to use the non abbreviated form, see the following for example:

I can't tell

Becomes:

I can not tell

Which is just fine.

So is Babies love skin on skin – can't you tell? a valid usage of the word can't? Why is this?

Answer

Can't is widely considered an abbreviated form of 'cannot', and 'cannot you tell?' is a grammatical expression.

Most contractions represent the joining of two words. “Can’t” is an
exception however. Following the rules that apply to most
contractions, you probably find yourself tempted to replace “can’t”
with “can not.” However, when replacing “can’t,” use “cannot.”

Cannot or can not (Writing Guides)

Both cannot and can not are acceptable spellings, but the first is much more usual. You would use can not when the ‘not’ forms part of another construction such as ‘not only’. For example:

These green industries can not only create more jobs, but also promote
sustainable development of the land.

Cannot or can not (Oxford)