Wash lemons and peel off all the zest using a vegetable peeler; set peeled lemons aside. Add lemon zest to a bowl and cover with sugar; toss to combine. Cover and let sit for a minimum of 2 hours, or up to overnight.
Bring water to a boil in a pot over high heat; turn off heat and pour in lemon-sugar mixture. Stir and let sit until sugar is completely dissolved, about 5 minutes.
Pour through a mesh strainer back into the same bowl and discard the zest. Let cool to room temperature, 20 to 30 minutes.
Cut lemons in half and squeeze juice into the bowl. Pour lemonade into a serving pitcher; cover and chill thoroughly before serving over ice, at least 2 hours.