Increase chillie powder or pepper powder to neutralize the taste of tamarind in a dish. You can also use potato to reduce the taste of tamarind. You can also use some extra water. Small pinch of tamarind is enough for a dish.
You don't exactly neutralize it. Neutralization is a specific reaction involving acids and bases (see the Related Questions to the left). You can remove the salt by various desalination processes, such as distillation or reverse osmosis.