Preheat the oven to 425°F (220°C).

Arrange tomatillos (stem side down) and onion quarters (skin side down) on a large rimmed baking sheet. Wrap garlic cloves in a small piece of aluminum foil and place the foil pouch in one corner of the baking sheet.

Bake at 425°F for 20 minutes or until the tomatillos and onions begin to char and soften. Transfer the baking sheet to a wire rack to cool. When cool enough to handle, place in a food processor. Do not peel the roasted tomatillos; puree them whole.

Add lime juice, chipotle peppers, and salt to the food processor. Process until pureed.

Transfer the mixture to a large stainless steel or enameled saucepan. Bring to a boil, then remove from heat.

Ladle hot salsa into hot jars, leaving half an inch of headspace. Remove air bubbles, wipe jar rims, center lids on jars, and adjust bands to fingertip-tight.

Place jars in a boiling water canner. Process for 25 minutes, adjusting for altitude. Turn off heat, remove lid, and let jars stand for five minutes. Remove jars and cool.