Wash tomatoes, core, cut in half and place cut side up on large rimmed ungreased baking sheet.
Leave onion peeled, cut in fours, add to baking sheet skin sides down.
Peel garlic cloves, seal in a small piece of tin foil, add to baking sheet.
Bake until tomatoes and onion start to get soft, and brown a bit. Remove baking sheet from oven and let cool.
Heat an ungreased frying pan (e.g. cast iron or a griddle) until very hot.
Rinse dried chiles and pat dry.
Put the dried chiles in the pan, and let each side toast for about 10 seconds, or until they just start to puff. (Don't allow to scorch.)
Put them in a bowl and cover with the boiling water to soften -- about 15 to 20 minutes.
Remove peels on roasted veg and add put them all into a food processor bowl.
When the chiles are soft, drain but reserve water. Remove the stems, rip them open and swish them in the water to rinse off the seeds. Add the chiles (not the water) to the food processor bowl .
Add lime juice to the food processor bowl.
Whiz the mixture in the food processor until smooth.
If desired, Ball says you may add a bit of the chile soaking water to thin the mixture a bit. Discard the rest of the water.
If desired, adjust taste with salt and pepper.
Put salsa in a pan and reheat on stove OR put in microwave-safe jug or bowl and zap until piping hot.
Ladle sauce into heated jars, leaving 2 cm (½ inch) headspace.
Debubble, adjust headspace.
Wipe jar rims.
Put lids on.
Process in a water bath or steam canner.
Process jars for 25 minutes; increase time as needed for your altitude.