Read the pressure-canner manufacturer's instructions and the linked NCHFP pressure-canning guide. Wear gloves while handling hot peppers and keep your hands away from your face and eyes.

Wash and dry the chiles. Slit each one so steam can escape. Blister skins for 6–8 minutes in a 400°F oven or broiler, or over a burner protected by heavy wire mesh. Cool under a damp cloth, peel, discard seeds and chop.

Wash the tomatoes. Dip them in boiling water for 30–60 seconds, until skins split, then transfer them to cold water. Slip off skins, remove cores and chop coarsely.

Combine the prepared tomatoes and chiles with the onions, salt, oregano and vinegar in a large saucepan. Bring to a boil, cover and simmer for 10 minutes.

Fill hot jars with hot sauce, leaving 1 inch headspace. Release trapped air, restore headspace, wipe rims and fit lids.

Dial-gauge canner: process pints for 20 minutes or quarts for 25 minutes at 11 psi from 0–2,000 feet; 12 psi at 2,001–4,000 feet; 13 psi at 4,001–6,000 feet; or 14 psi at 6,001–8,000 feet.

Weighted-gauge canner: process pints for 20 minutes or quarts for 25 minutes at 10 psi from 0–1,000 feet or 15 psi above 1,000 feet.

When processing ends, turn off the heat and let the canner depressurize naturally. Do not force cooling. Follow the canner manufacturer's opening directions, then lift jars upright and cool undisturbed for 12–24 hours before checking seals.