Add the tea bag and water to a glass measuring cup that holds at least 1 cup. Brew the tea for 10 minutes. When cool enough to handle, squeeze the tea bag over the tea to capture optimum potency, and then discard the bag.

Pour the tea into a cocktail shaker. Add the sweetener, liqueur, lime juice, and ice cubes. Shake until chilled. Strain into a 10-ounce highball glass or an 8-ounce martini glass. Garnish with the lime slice. Serve immediately.