Squeeze the lemons to extract fresh lemon juice.
In a pitcher, combine the lemon juice and sugar.
Stir until the sugar is completely dissolved.
Gradually add cold water to the pitcher, mixing well.
Taste the lemonade and adjust sweetness if desired.
Refrigerate for at least 30 minutes to chill.
Prepare serving glasses with ice cubes.
Pour the chilled lemonade over the ice.
Garnish with fresh lemon slices.
Serve immediately and enjoy!