Add the water and sugar to a large pot over medium-high heat. Bring the mixture to a boil and cook until all the sugar is dissolved.
While the mixture is on the stove, begin to cut and juice lemons (about 6-8 lemons, depending on size) into a clean measuring cup.
In a food processor, blender, or single-cup blender, blitz the strawberries until completely smooth. If the strawberries are not blending well, try adding a ladle full of the water/sugar mixture and blend again.
Using a sieve, strain the pureed strawberries into a clean bowl or cup. You may discard the seeds and large pulp pieces.
Once the sugar is fully dissolved, remove from heat. Stir in the lemon juice and strained strawberry puree. Stir until combined and transfer to the pitcher.
Place in the refrigerator for at least 2 hours to cool down. When kept cool, the lemonade will keep for several days.
Notes
If at all possible, please use fresh lemons! Bottled lemon juice is just not the same.