Step 1

Wash the tomatoes well under clean, running water.

Step 2

Place a large stainless steel saucepot on the stove. Cut about six tomatoes into quarters, place these in the pot, and begin heating over medium-high heat. Crush the tomatoes with the back of your spoon once they soften.

Step 3

Cut the remaining tomatoes into half and add to the pot as your work. Stir frequently to cook evenly and prevent sticking.

Step 4

When all tomatoes have been added, continue to cook, while stirring occasionally, until tomatoes are soft and juicy, about 10 minutes.

Step 5

Remove the pot from the heat and let the tomatoes cool slightly before straining.

Step 6

Puree the tomatoes using a food strainer, food mill, or sieve to remove skins and seeds.

Step 7

Return the tomato puree to the saucepot and simmer uncovered over medium-low heat until the sauce thickens and is reduced by half, about 15 to 30 minutes. Stir occasionally to prevent sticking.

Step 8

While the tomato sauce is cooking, wash the jars, lids, bands, and canning tools in warm, soapy water. Rinse thoroughly, and set aside to air dry on a clean kitchen towel.

Step 9

Place the water bath canner on the stove. Place the jar rack into water bath canner, set the jars in the canner, and fill with enough water to cover the jars.

Step 10

Bring the canner to a simmer (180˚F) for 10 minutes, and keep the jars hot until you are ready to fill them.

Step 11

Spread a kitchen towel on the counter. Use the jar lifter to remove a jar from the canner. Drain the water back into the canner, and place it on the towel. Keep the remaining jars in the canner so they stay hot.

Step 12

Add 1/2-teaspoon citric acid or 2 tablespoons lemon juice to each quart sized jar (1/4-teaspoon citric acid or 1 tablespoon lemon juice for pints).

Step 13

If using salt, add up to 1 teaspoon for each quart, and 1/2 teaspoon per pint.

Step 14

Use the canning funnel and ladle to fill the jar with the tomato puree. Leave a 1/2-inch headspace.

Step 15

Wipe the rim to remove any residue, center a lid on the jar, and screw on a band until it is fingertip tight.

Step 16

Use your jar lifter to place the jar back into the canner, and repeat with the remaining jars. Try to leave a little space in between the jars.

Step 17

Once all the jars are in canner, adjust the water level so it is two inches above the jar tops. If you need to add water, pour hot water around the jars and not directly on them.

Step 18

Cover the canner and bring to boil over high heat. Once water boils vigorously, continue boiling quart size jars for 40 minutes (35 minutes for pint jars) at altitudes of less than 1,000 feet. Adjust processing time for your altitude if necessary (See note below).

Step 19

When processing time is complete, turn off the heat, remove the cover, and let the canner settle for about 5 minutes.

Step 20

Spread a dry kitchen towel on the counter. Remove the cover by tilting lid away from you so that steam does not burn your face.

Step 21

Use the jar lifter to remove the jars from canner and place on the towel. Keep the jars upright, and don't tighten bands or check the seals yet. Let the jars sit undisturbed for 12 to 24-hours to cool.

Step 22

After 12 to 24-hours, check to be sure jar lids have sealed by pushing on the center of the lid. The lid should not pop up. If the lid flexes up and down, it did not seal. Place the jar in the refrigerator and use up within a week, or place the puree into freezer containers and freeze for up to 6 months.

Step 23

Remove the screw on bands and wash the jars. Label, date, and store your jars in a dark, cool place (50 to 70 F). Use within 12 to 18 months for the best quality and flavor. Once the jar is open, refrigerate and use up within a week. Yields about 7 quarts of tomato puree.