For now, even manual curation works. You can broadcast recipe events to your relay, whether that's just you and your team, or your users. Minimal incentives like getting back the sats they spent on the relay could help as well. By default, searching those words to just your relay and/or the user's relays mitigates the spam. Automated discovery from the wider nostr ecosystem can come as infra evolves. Lot's of behind the scenes projects, I'm even working on one. I think when those projects are ready, that's when you should consider looking at that level of openness. Because otherwise, you're stuck with things that can be broken easily like key words and hashtags. Thinking it through, I think there are two things to keep in mind to balance out a quality community with discovery. 1) start however small and narrow you need so you can guarantee a good experience. If you can keep quality high by follows of follows (possibly further) from zap.cooking users, that's a lot already. Keywords and hashtags have the most effectiveness when you're confident in the sources you're pulling from. 2) Every step you take looking into the open nostr ecosystem opens you up to more potential bad experiences, so you need to deeply consider every step you're making, because what you display from your app is representative of the community you're cultivating.

There's no reason not to limit those requests to trusted relays that host clean content. You could also maintain a list of foodie npubs, and/or your team and committed users (or a bot) could scan wider swath of the network & republish content... then blend these things into a feed with the client's home relay. Continuing to pull directly from public-to-write relays for the main feed invites in spammers, which is a much worse experience for everyone than some new user not having a first post seen because it chases off the lurkers, too. More and more, existing users are withdrawling themselves from public relays and blocking them because they don't want to get spammed themselves or they don't want their notes to be associated with the nasty stuff that ends up hosted there. If someone wants to see those notes, they can follow the spammy & nasty authors, who, by sane metrics, should be forced by the network into running their own relays for that stuff. That's kind of, in a strange way, the whole point of all this. Curated feeds should be strict and strongly opinionated, that's what makes them interesting and nice to browse. It's just really a shame to me that things like porn will randomly show up in a cooking app when simple preventative solutions exist and work.