。
This is a highly recommended restaurant.
Literal
This [topic-は] one-push [genitive-の] restaurant [copula-なんだ].
一押し ('highly recommended, top pick,' literally 'one-push') is a modern idiom describing the item you most want to recommend — often seen in review websites, menus, and shopping contexts. なんだ at the end is the explanatory なのだ, suggesting 'the thing is, this is X.' Casual, warm recommendation style.