made this my comments
long description so skip if you get bored.
The recipe came out better than expected but I did have challenges with the monk fruit.
I used Monk Fruit which is erythritol. To me it seems quite a bit sweeter than regular sugar so in the future I would use less. A lot less if I could get away with it. I'm not into super sweet anything.
I did not know what to expect making caramel with this, so I put just the monk fruit on medium heat and nothing was happening for quite a while then suddenly and almost instantly most of it liquefied. So I added the water and another "instant" weird chemical reaction as part of it turned solid in these big lumps and stuck to the pot like crazy glue.
So my whisk did nothing for these big lumps so I got a butter knife and chipping away at it trying to salvage it. Slow going so I tried raising the heat. Not sure if that did anything. So I added the butter. I turned the heat down and eventually I got most of the lumps chipped away and they broke down into the rest.
But after several minutes still not turning golden as the recipe stated. So I turned the heat up a bit. Finally got a little color but not "goldenizing" if that is a word... So I turn the heat down and just let it sit for a while. Nothing much happens I come back. But I see the butter is kind of breaking down into brown specs. (Brown not gold) So I'm worried it is just ruined and will taste burnt.
It never really thickened to a point where I would be satisfied but I poured it in the ramekins.
When it came time to put in the custard it made exactly four ramekins. One of them came out perfect where the caramel stayed on the bottom the other 3 kind of mixed with the custard as I poured it in.
End result after baking and refrigeration was a pretty good (keto) flan. A little too sweet for me but everyone else enjoyed it. I've had flan where the top was more of a liquid than the crispy sugar like on a creme brulee but in this case it was more crispy sugar. It did not taste burnt butter as I feared.