Boil 4 cups of filtered water in a medium-sized pot over medium-high heat until it reaches a rolling boil.

Remove the pot from heat. Add 3-4 black tea bags, several fresh rosemary sprigs, the zest of the orange, and thinly sliced ginger. Stir gently.

Let the mixture steep for 5-7 minutes, then remove tea bags to avoid bitterness.

Stir in sugar to taste when the tea is warm, then set aside to cool slightly.

Strain the mixture into a large pitcher using a fine mesh strainer.

Squeeze the juice from the freshly zested orange into the pitcher, stirring well.

Cool to room temperature before refrigerating for at least 2 hours.

Serve over ice cubes and garnish with orange slices and rosemary sprigs.