Add the water, cherries, blueberries, lemon juice and sweetener in a pan on the stove over medium heat.
Use a hand blender to break up the mixture fully into a liquid.
Allow it to come to a boil, after about 5-6 minutes. Once boiling, turn the heat off.
Let this mixture cool down for 30 minutes at room temperature.
After 30 minutes, using a sieve, pour the mixture into a pitcher. Press the mixture down well into the sieve to strain all the juice out from any berry chunks remaining. Place in the refrigerator.
When ready to serve, add ice to 3 cups, then pour the lemonade mixture on top of each.
Serve cold!
Notes
Storage
Store in a covered pitcher in the refrigerator for up to two days.