Drain the can of whole tomatoes in a strainer set over a bowl to catch the juices. If the tomatoes look full (i.e. whole and intact), press on them a bit to release more.
Finely chop the white onion, jalapeño (removing the seeds if you wish), and garlic. Add to a blender or food processor with along with the cilantro and salt and grind the pieces a bit smaller.
Add the drained tomatoes and lime juice and pulse the machine until you get your desired salsa consistency.
If the mixture seems too thick, add some of the reserved tomato juice, a tablespoon at a time.
Adjust seasoning to taste.
Pour into a bowl and eat right away. Leftovers will keep for up to 1 week in the fridge.