[RadioKid]

"こんやがおいしい：KON'YA GA OISHII; It is tasty tonight"

Does it make sense in English? Does it mean "it is not tasty on other days"?

I can not understand well why you need to refer to "tonight" but if you need the word "tonight" and not want to emphasize it, you can omit both "GA" and "HA/WA". I mean you can say "KON'YA OISHII" though I can not find how it sounds in your situation.

"OISHII" sometimes means rather "nice" than "delicious". In this case, "KON'YA GA OISHII" makes sense as "it must be tonight, no other day than today" when it is someone's birthday or some anniversary.

I'm sorry if I misunderstand your question.