Take a large stainless steel pot. Put in it the cranberries, onion, and garlic.
Put pot on stove over high heat and bring to the boil, stirring, then reduce to a steady simmer for 10 minutes or until the cranberries are soft and have popped.
Remove pot from stove.
Process mixture a batch at a time through a food processor or blender to make it smooth.
Put blended mixture back into a pot.
Add the ingredients from the dry mustard down to and including the cayenne pepper.
Put pot back on stove, and bring back to a boil, stirring. Lower to a simmer and let simmer uncovered for about 30 minutes or until the mixture mounds up on a spoon in a way that ketchup would.
Stir in stevia, adjust taste with a tidge more or less if desired.
Pour into quarter-litre (½ US pint / 8 oz) jars.
Leave 2 cm (½ inch) headspace.
Debubble, adjust headspace.
Wipe jar rims.
Put lids on.
Process in a water bath or steam canner.
Process either size jars for 15 minutes; increase time as needed for your altitude.