Cut the strawberries into small pieces and place them in a saucepan with the lemon juice, water, and sugar. Bring to a boil, stirring occasionally.
Once it reaches a boil, reduce the heat and let it simmer for about 5 minutes. Stir regularly. The strawberries will break down and form a chunky sauce.
For a smooth strawberry sauce, blend the mixture using an immersion blender. If you prefer a bit of texture, simply mash the sauce with a fork.
Tips
For extra lemon flavor, you can also add some lemon zest (just the yellow part of the peel) while cooking the strawberries.