Wash the tomatoes, core, and remove any bad spots. To make peeling easier, cut an X shape on the bottom of the tomatoes. Then add them to boiling water to blanch them, which helps remove the skins. Boil for about one minute. Then put them in ice water. When cool enough to touch, remove the skins by pulling them off.
Measure the tomatoes after peeling and coring them. Place the tomatoes into a large, thick-bottom pot for cooking.
Add the onion, bell pepper, jalapeno, garlic, cilantro, salt, cumin, and vinegar to the pot. For mild salsa, remove the seeds and membranes from the jalapenos. For hotter salsa, leave the seeds and membranes. This is also the time to add any other hot peppers if you want to use them. Stir.
Cook for 1 hour with a lid propped on top of the pan. Stir occasionally. After 1 hour of cooking, stir the salsa. Check the consistency of the salsa. If the salsa is too runny, cook in 15-minute increments until it reaches the desired thickness. If necessary, remove the lid to hasten the evaporation of liquid.
To give the salsa a fine texture, use an immersion blender in the pot and blend until all the tomato pieces are broken down.
Place simmering hot salsa in hot jars fresh from washing in the dishwasher. Alternatively, heat clean, wet jars in the oven at 275°F for 20 minutes to sterilize them. Add simmered lids and rings to the jars.
Add simmered lids and rings to the jars.
Use a water bath to process the salsa in canning jars for 15 minutes. See the note below for processing times for altitudes exceeding 1,000 feet.