- Bring a large saucepan of water to a boil.
- Mark a shallow X on the bottom of each tomato.
- Blanch tomatoes in boiling water about 1 minute until skins loosen. Remove tomatoes from water and set aside to cool. Peel off the skin; it will come off easily.
- Remove seeds and cut tomatoes into cubes. Set aside.
- In a large saucepan, sauté onion for 3 to 4 minutes.
- Add peppers and jalapeño and fry for 3 to 4 more minutes.
- Add garlic and fry 2 to 3 minutes.
- Add reserved tomatoes, lemon juice, vinegar, cumin, salt, and pepper.
- Let simmer for 25 to 30 minutes. Add cilantro.
- Pour salsa into sterilized Mason jars, filling them 1 cm (1/2 inch) from the top. Seal and sterilize.
This recipe's acidity level means it can be canned using the boiling water technique.
- Sterilize jars by immersing in boiling water for about 5 minutes. The lids must be new to ensure a proper seal. Soak lids in hot water before using.
- Fill jars, leaving a headspace of about 1 cm (½ in.).
- Place lids and screw bands on jars but do not over-tighten.
- Immerse jars in boiling water and boil for at least 15 minutes.
- Remove jars from water and let rest for 24 hours. The lids will be depressed and make a sudden popping noise when the seal is tight.
- The jars can be stored for one year in a dark, dry, cool place.