Combine the rosemary and water in a saucepan, and bring it to a boil. Lower the heat and let it gently simmer for 1 to 5 minutes. The longer to simmer it, the more potent the rosemary flavor will be.

When it's done simmering, use a slotted spoon to remove the rosemary and any leaves that may have fallen off.

Pour the strained tea into 2 mugs and serve. If you're only cooking for 1, store the other half of the tea in an airtight container in the fridge for iced tea later or reheat for a warm beverage.