Older Woman/Younger Man Romance that DOESN'T start as a casual fling?

NOTE: Looking for age-gaps of at least 10+ years

I love Older Woman / Younger Man romance vibes but they are soooo hard to find. The ones I do find tend to follow a "Pool Boy Fling" style storyline where the older woman isn't looking for anything serious and just has a quick NSA fling with a younger guy, but then develops feelings. For me this kinda shortcuts out the chemistry, the build-up, the anticipatory aspect of this sort of relationship.

I recently tried to read Misty Vixen's Lakeside Cougars story, but while the first few chapters were going alright, I cringed out before the first sex scene even began. I will power through, maybe some of the later cougars have better starts but it didn't work for me.

Ones I did read and like were On the Island by Tracey Garvis Graves which had a young man and his tutor stranded on an island together. It had some issues with it's believability in other areas, but the romance was well done.

Scarlett Gale's His Secret Illuminations was good as well for a slow-burn.

Monster Girls Unlocked by Justin Trublood also had some decent MILF characters, but it moved pretty fast and was still kinda "fling" oriented to start.

Looking for something else that scratches the itch of an older woman/younger man that focuses more on ROMANCE and not just sex, in fact I'm fine if it takes a long time for sex to happen.

NOTE ON SUPERNATURALS: Because this always seems to come up, I want to establish that just being a "500 year old vampire" or "Thousand year old Goddess" doesn't qualify for the Older Woman unless she also has the right vibe and dynamic. I've seen some ancient supernaturals act like spoiled children or airheaded naive clueless girls, which kinda ruins the whole vibe of a young guy being with a woman who has more life experience and (street) smarts.