Using a medium saucepan, combine strawberries, water, sugar, and lemon juice. Simmer slowly for ten minutes; this will help to thicken the sauce.
Transfer to a blender and purée until smooth.
Store in an airtight container and refrigerate. This can last for up to 5 days in the fridge.
Notes
The sweetness of strawberries will vary, so add more sugar if desired.
For a thinner sauce, add more water.
For a thicker sauce, put the pureed coulis it back in the pan and simmer for few minutes until you reach the coating consistency. Thicker coulis work well when topping buttercreams or frostings.