This is the word in IPA: /rɛstʉˈrɑŋ/. Some in Norway have proposed alternative spelling such as resturan (pronounced like "resturang") to more closely match its pronunciation.
Makes sense from an etymological standpoint. The word comes from French, where the -nt isn’t pronounced, but the final a is a nasal vowel because of the lost n. I assume this sounded to norwegian ears like aŋ, so they pronounced it that way.