It should be frozen to be absoloutely sure it would be safe. Even pressure canning something unless the recipe is tested can be unsafe.

I am posting a tested safe recipe. As you can see, it warns against adding any additional amounts of onions, peppers, etc.

SPAGHETTI SAUCE WITHOUT MEAT

30 lb. tomatoes
1 cup chopped onions
5 cloves garlic, minced
1 cup chopped celery or green pepper
1 lb. fresh mushrooms, sliced (optional)
4-1/2 tsp. salt
2 tbsp. oregano
4 tbsp. minced parsley
2 tsp. black pepper
1/4 cup brown sugar
1/4 cup vegetable oil

YIELD: About 9 pints

PROCEDURE: CAUTION: DO NOT INCREASE THE PROPORTION OF
ONIONS, PEPPERS OR MUSHROOMS.

Wash tomatoes and dip in boiling water for 30 to 60 seconds or until skins split. Dip in cold water and slip off skins. Remove cores and quarter tomatoes. Boil 20 minutes, uncovered, in large saucepan. Put through food mill or sieve. Saute onions, garlic, celery or peppers, and mushrooms (if desired) in vegetable oil until tender. Combine sauted vegetables and tomatoes and add remainder of spices, salt and sugar. Bring to a boil. Simmer, uncovered, until thick enough for serving. At this time the initial volume will have been reduced by nearly one-half. Stir frequently to avoid burning. Fill hot jars, leaving 1-inch headspace. Adjust lids and process.

RECOMMENDED PROCESS TIMES FOR SPAGHETTI SAUCE WITHOUT MEAT IN A DIAL-GAUGE PRESSURE CANNER

Style of Pack: Hot. Jar Size: Pints, Quarts.
Process Time: 20 minutes for Pints, 25 minutes for Quarts.
Canner Gauge Pressure (PSI) at Altitudes of:
0 - 2,000 ft: 11 lb.
2,001 - 4,000 ft: 12 lb.
4,001 - 6,000 ft: 13 lb.
6,001 - 8,000 ft: 14 lb.

RECOMMENDED PROCESS TIMES FOR SPAGHETTI SAUCE WITHOUT MEAT IN A WEIGHTED-GAUGE PRESSURE CANNER

Style of Pack: Hot.
Jar Size: Pints, Quarts.
Process Time: 20 minutes for Pints, 25 minutes for Quarts.
Canner Gauge Pressure (PSI) at Altitudes of:
0 - 1,000 ft: 10 lb.
Above 1,000 ft: 15 lb.