Mix the one cup of warm water with 1 cup of sugar in a small pot over medium heat. Stir until the sugar is dissolved and the liquid is simmering. Remove from heat and let cool.
Juice lemons. Mix lemon juice with simple syrup mixture.
Add raspberries to a food processor blender and process until smooth.
Add raspberry pulp to a strainer. Pour lemonade mixture through strainer. It should pick up lots of raspberry color and juice. Repeat a few times. You should be left with mostly seeds in the strainer.