1. Wash, remove stems, and trim tomatoes of any bruised or discoloured parts.

2. Working quickly and with 1 lb. of tomatoes at a time, quarter the tomatoes and place in a large saucepan.

3. Bring the tomatoes to a boil as you crush them with a potato masher or large spoon.

4. Continue adding the quartered tomatoes, cutting them up as you work.

5. Keep mashing the tomatoes over high heat until all pieces have been added.

6. Let the tomatoes simmer for 1 hour, stirring as needed to prevent the tomatoes from burning or sticking to the bottom of the saucepan.

7. Transfer the thickened, crushed tomatoes to a food mill or sieve and remove skins and seeds.

8. Return the tomatoes back to the saucepan. Add the citric acid and stir until completely combined with the crushed tomatoes.

9. Add up to 1 teaspoon of pickling salt, the bay leaves, and garlic clove (if using).

10. Continue to cook the tomatoes over medium heat, stirring frequently, for another 2 1/2 hours (or until the tomato mixture has been reduced by half).

11. As the tomato paste thickens, prepare a boiling water canner, 2-part lids, and half-pint jars.

12. When the tomato paste has reduced by half, distribute the hot tomato paste among the heated jars, leaving 1/2-inch headspace.

11. Seal each jar with 2-part lids and process in a water bath canner for 45 minutes, adjusting the time as needed depending on the altitude.

12. Turn off the heat and give the processed jars 5 minutes to acclimatize before transferring them to a clean towel (use a jar lifter if you one). This extra 5 minutes allows them to cool slightly before they're removed from the canner, and helps prevent siphoning.

13. Arrange the jars lid-side up, without touching, and let them sit for 12 to 24 hours at room temperature.

14. Remove the rings and check to make sure the lids are sealed. Move any unsealed jars to the fridge.

15. Label jars with the date and contents. Properly canned and sealed jars should maintain quality on the pantry shelf for 12-18 months. Store in the refrigerator once opened.