Start by bringing 4 cups of water to a rolling boil in a medium saucepan.

Once boiling, remove the saucepan from heat and add the tea bags. Allow the tea to steep for about 5-10 minutes.

After steeping, remove the tea bags and stir in 1 cup of granulated sugar while the tea is still warm.

If using, stir in the vanilla extract now.

Let the tea come to room temperature before transferring it to a heat-resistant pitcher.

Place the pitcher in the refrigerator until the tea is completely chilled, about 1-2 hours.

Fill glasses with ice and pour the chilled tea over the top.

Add a slice of lemon to each glass if desired.