Put the bacon and onion in a large non-stick frying pan over medium heat.
Cook for 5 minutes, stirring now and then, until the bacon fat has run and the onion is soft.
Add the golden monkfruit sweetener, thyme, keto maple syrup, red wine vinegar and espresso.
Stir until everything is combined.
Cook for about 15 minutes, stirring now and then, until the jam is thick and sticky. When you drag your spoon through it, it should leave a clear trail on the base of the pan.
Store
Spoon the jam into a clean airtight jar.
Leave it to cool, then put it in the fridge within 2 hours.
Notes
Fridge: refrigerate within 2 hours, keep at 5°C or below and eat within 1 week. Freezer: up to 3 months. Thaw in the fridge, use within 24 hours and don't refreeze. Each serve is about 2 tablespoons. Key swap: frozen chopped onion and bacon pieces skip the chopping.