Okay, so you're looking for Sakura x Naruto stuff. Honestly, I used to hunt for this ship everywhere because, let's be real, it's pretty underserved next to all the NaruSasu and SasuSaku out there. AO3 is your absolute best bet for quality and tagging. Just filter the 'Naruto' fandom, then put 'Uzumaki Naruto/Haruno Sakura' in the relationship tag. You'll find some real gems there, especially longer slow-burns that actually develop their friendship into something believable.
For a totally different vibe, I'd sometimes poke around Fanfiction.net. The search is a nightmare, but I've dug up some classic, pre-2010 fics there that have a certain nostalgic charm. The writing quality can be super hit-or-miss though, so maybe sort by favorites or reviews. Also, a weird tip: check out some dedicated Naruto fanfiction forums or subreddits. People sometimes post links to their own hosted sites or Google Docs for fics that might not be on the big platforms. It feels like a little treasure hunt.
Just a heads-up, if you're searching on any site, avoid the 'NaruSaku' tag on AO3—that's for platonic friendship. You want the one with the slash.