In a microwave-safe glass measuring cup, add 2 cups of water with 3-4 black tea bags. Microwave for 2 minutes. Remove from microwave and let tea steep for about 5-10 minutes.
Discard tea bags and pour tea into a pitcher. Add 2 more cups of cold water to tea and stir.
In a separate container, combine 3/4 cup lemon juice, 1/2 cup granulated sugar, and 3 1/4 c. cold water. Stir until all the sugar is dissolved.
Pour the lemonade into a pitcher with the tea mixture and stir to combine. Chill for at least 1-2 hours.
When ready to serve, pour into glasses over ice and garnish with mint if desired. Keep refrigerated.
Notes
For a sweeter tea, increase the amount of sugar to 3/4 cup. For a less sweet tea, you can reduce the sugar to 1/3 cup.For a spiked version add 1 oz. of bourbon or lemon-flavored vodka per glass.