Put chopped strawberries, sugar, and 2 tablespoon water to a small saucepan over medium heat.
Cook for 7-9 minutes, stirring occasionally, until strawberries are very soft and the liquid is bright red and glossy. The consistency should be loose and saucy; not jammy.
In a small bowl, stir ¼ teaspoon cornstarch with the remaining ½ teaspoon water until completely smooth.
Once the strawberries are softened, stir the cornstarch slurry into the mixture and let it gently simmer for about a minute, until just slightly thickened. Avoid boiling or cooking too long as mixture may get gummy.
Remove from heat and stir in the lemon juice and pinch of salt.
Let puree cool slightly, then blend until completely smooth using either a blender, handheld immersion blender, or food processor.
Strain mixture through a fine-mesh sieve, pressing firmly with a wooden spoon to extract as much puree as possible.
Store strawberry puree in an airtight container in fridge and let cool completely before using. Purée should stay fresh for about 5 days when stored properly.