As far as the original question, my guess is that it is simply a convention for certain verbs that is nevertheless sometimes broken. It is standard to say, "I really like this book," but you do sometimes hear people say "I'm really liking this book."
Occasionally, we might say, "this soup is tasting delicious." This might be especially in cases where you have had that same soup many times, and you are emphasizing that it is especially good this time.
"Mom, this soup is tasting extra delicious today! Did you add new spices?" (although note, "tastes" works just as well here).
In your example, you are using tasting intransitively but, more importantly, it is a "stative" verb, meaning it describes the state of the food. There is extensive discussion of the use of present continuous forms with such verbs here : I'm loving it.
It's not because it is an intransitive verb - come is an intransitive verb but we can say "Are you coming?".
Taste is one of a series of verbs of sensation, like feel, sound, look, smell which can be used as linking verbs (like be) which are not usually used in continuous when talking about the senses, but can also be used when talking about actions or experiences, when we can use continuous. These are sometimes transitive, sometimes intransitive
This cake tastes delicious. - sense - linking What's she doing? She's tasting the cake to see that it's OK. - action - transitive
This cheese smells off. - sense - linking What are you doing? I'm smelling this new perfume. - action - transitive
Those strawberries look delicious. - sense - linking She was looking round the room. - action - intransitive
This sweater feels warm - sense- linking How are feeling today? - experience - intransitive
Keep this quiet, but sometimes we do use continuous with these sense verbs (and other state verbs not usually used in continuous), when we are talking about 'right now' or informally. "How's the cake tasting?" but don't use it in a test! That's why McDonald's 'I'm lovin' it' works.
I can imagine situations where not only is using taste in the present continuous correct, but - to me - better yet [than taste in the simple present]. Imagine a woman who really hates chicken livers but one day her husband prepares it in a different way, adding many vegetables and some special sauce. The woman might say, "Yah, it is [emphasized] tasting yummy yet I bet next time around my hate towards this will return, thank God you've put many vegetables on top so I can't see those livers!".
No I don't think so. She would say "Yes, it does taste delicious like this way but I'm still not sure that I would like them again". I do + verb is not all that common but is used for emphasis. "I do like this" emphasises the fact that one likes it, one would not say "I am liking this".