Leave it on the heat longer. The water will evaporate.
you can add some cornstarch to the salsa while it is heating. Mix some cornstarch with a little bit of water to desolve and remove any lumps then add it to the salsa and stir it it will begin to thicken.
Other people asked questions on similar topics, check out the answers they received:
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them