Place 7 clean 500 ml mason jars on a rack in a boiling water canner. Cover jars with water and heat to a simmer (180°F/82°C). Set screw bands aside. Keep jars hot until ready to use. Preheating Bernardin® lids is not advised.

The sealing compound used for our home canning lids performs better at room temperature than it does pre-heated in simmering water (180°F). Simply wash lids in hot, soapy water, dry, and set aside until needed.

Preheating can lead to less vacuum being achieved during water bath canning, and to buckle failures during pressure canning. Peel, core and coarsely chop tomatoes.

Combine 20 cups (5000 ml) chopped tomatoes, onion, garlic, oregano, bay leaves, salt, black pepper, red pepper and sugar in a large stainless steel saucepan. Stirring occasionally, bring to a boil; boil until desired consistency is reached, about 2 hours.

Press tomato mixture through a fine sieve or food mill; discard seeds. Return tomato sauce to saucepan; cook over medium heat until thickened, stirring occasionally. Place 1 tbsp (15 ml) of lemon juice into a hot jar. Ladle sauce into a hot jar to within 1/2 inch (1 cm) of top rim (headspace).

Using nonmetallic utensil, remove air bubbles and adjust headspace, if required, by adding more sauce. Wipe jar rim removing any food residue. Centre hot sealing disc on clean jar rim. Screw band down until resistance is met, then increase to fingertip tight. Return filled jar to rack in canner.

Repeat for remaining sauce. When canner is filled, ensure that all jars are covered by at least one inch (2.5 cm) of water. Cover canner and bring water to full rolling boil before starting to count processing time. At altitudes up to 1000 ft (305 m), process -boil filled jars - 35 minutes.

When processing time is complete, remove canner lid, wait 5 minutes, then remove jars without tilting and place them upright on a protected work surface. Cool upright, undisturbed 24 hours; DO NOT RETIGHTEN screw bands. After cooling check jar seals.

Sealed discs curve downward and do not move when pressed. Remove screw bands; wipe and dry bands and jars. Store screw bands separately or replace loosely on jars, as desired. Label and store jars in a cool, dark place. For best quality, use home canned foods within one year.

Processing: At altitudes up to 1000 ft (305 m), process -boil filled jars - 35 minutes - 35 minutes.

Altitude-adjusted processing table: At altitudes up to 1000 ft (305 m), process -boil filled jars - 35 minutes