How can I safely use pressure canning to preserve tomatoes?

To safely use pressure canning to preserve tomatoes, follow these steps:

1. Wash and prepare the tomatoes.
2. Fill jars with tomatoes, leaving proper headspace.
3. Add lemon juice or citric acid to each jar to ensure acidity.
4. Seal jars with lids and rings.
5. Place jars in a pressure canner with the appropriate amount of water.
6. Process jars at the recommended pressure and time for your altitude.
7. Allow jars to cool, check seals, and store in a cool, dark place.