Remove and discard the cores from the tomatoes and the stem from the jalapeño. Then place the tomatoes and jalapeno in a small saucepan and add just enough water to cover. Bring to boil over medium-high heat, then reduce the heat to medium-low and simmer for approximately 15 minutes or until the skin has broken away from the tomatoes.

Drain the tomatoes and jalapeno and set them aside until cool enough to handle. Remove the skins from the tomatoes and add them to a blender along with the jalapeno. Pulse until roughly chopped.

Add the salt, chopped onion and cilantro. Purée until smooth. (This is not a chunky salsa.)

Taste the salsa and add additional salt, onion or cilantro if necessary. If the salsa is too spicy, boil another tomato or two and puree it into the salsa to moderate the heat. If you add more tomato, you may also want to add a bit more onion and cilantro, and it will certainly need a bit more salt. Serve with your favorite tacos, burritos, quesadillas or tortilla chips and enjoy!