Personally, I think using verbs related to senses in the continuous form is unnatural, unless we use them as action verbs instead of stative verbs. For example: The soup smells delicious. - here 'smell' is a stative verb so I wouldn't say 'it is smelling delicious' (unless I want to emphasize that it is temporary or there has been a change). However, you could use 'smell' as an action verb and then it is perfectly natural in the continuous form. For example: I am smelling perfumes to try to choose one I like. - here 'smell' is an action verb so it is natural to use it in the continuous form.

Hi Maria! Thank you for posting this. So generally we would use the regular present tense form, 'smells delicious' - for example, 'Wow, that smells delicious!' . However, colloquially (that is when we have informal everyday conversations), we could use the present continuous form' 'smelling delicious' in a fun and cheeky way - for example, 'Hey, that's smelling delicious chef!' to tell someone we know that they seem to be doing a good job cooking!

Your cooking looks funny, but so far it's smelling delicious. Your cooking looks funny, but so far it smells delicious. . Seems as if you can.

In your example we have to use “smells” delicious. There are occasions when we use the continuous form, for example our partner might be cooking some delicious food and then we can say “Mhmmmm” it’s smelling good!” However technically it would still be more correct to say: “ that smells good”.

"Smell" in this use is a state verb. It expresses a state of existence that's felt to be fairly enduring and consistent. For this reason, it doesn't usually occur in the continuous. There are a few obscure, informal uses of "smell" and other state verbs in the continuous, but you don't have to worry about these if you're learning functional Standard English.