Squeeze the lemons and pour the juice into a pitcher. Mix together the sugar with 3 cups water and stir to dissolve to make a syrup. Add the syrup to the lemon juice and top it up with 8 cups water. Taste to make sure it's sweet enough for you, and then add the raspberries. Mix the lemonade together and let chill in the fridge. (Keep in mind that the raspberries are tart, so be sure to sweeten enough!)
Fill mason jars with ice cubes and top them off with the lemonade.