In a 7- to 8-quart stainless-steel, enamel, or nonstick heavy pot heat butter and oil over medium heat. Add onions, carrots, celery, and garlic. Cook about 20 minutes or until vegetables are tender, stirring occasionally. Stir in tomatoes, sugar, and salt. Bring to boiling over medium-high heat, stirring occasionally; reduce heat. Simmer, uncovered, for 20 minutes.
Press tomato mixture through a food mill or sieve; discard skins and seeds. Return strained mixture to pot. Bring mixture to boiling; reduce heat. Simmer, uncovered, about 45 minutes or until reduced to about 10 cups. Remove from heat. Stir in basil, lemon peel, and lemon juice.
Ladle hot soup into hot sterilized pint canning jars, leaving a 1/2-inch headspace. Wipe jar rims; adjust lids and screw bands.
Process filled jars in a boiling-water canner for 35 minutes (start timing when water returns to boiling). Remove jars from canner; cool on wire racks. Makes 5 pints.