In a small pot add lemon juice on medium heat. It doesn't need to boil just get hot enough to melt sweetner. Add sweetener and whisk until it has dissolved then remove from heat
In a pitcher pour in lemon juice and sweetener. Add in 2 cups of water and begin tasting for your liking of how sweet or sour you'd like it to be.
At this point add 1/2 cup at a time while tasting to avoid watering the lemonade down. If the lemonade is hot while tasting it will appear "less" sweet than what it really is
You can follow the directions and add the full 3 cups but from my experiences making lemonade sometimes you have to adjust more or less with the water.