Wash the strawberries gently under cold water. Remove the green tops using a small knife. Cut large strawberries in half. Smaller ones can stay whole. Fresh and ripe strawberries give the best flavor.

Place strawberries into a medium saucepan. Add caster sugar, lemon juice, and water. Stir gently to combine everything. Make sure the sugar spreads evenly over the fruit.

Turn the heat to medium. Let the strawberries simmer gently for about five to seven minutes. Stir occasionally. The fruit will soften and release natural juices. The color will become deeper and glossy.

Remove the saucepan from heat. Let the mixture cool slightly. Use a blender or hand blender to blend until smooth. Be careful while blending warm mixture. It should become silky and bright red.

If you want a very smooth sauce, pour the mixture through a fine sieve. Use a spoon to press the sauce through. This removes seeds. Skip this step if you like a natural texture.

Let the coulis cool completely before storing. Pour into a clean jar or container. Keep in the refrigerator until needed. It thickens slightly as it cools.