Rinse fresh berries under cold water and pat completely dry with paper towels.

Place berries and filtered water into a medium saucepan over medium heat, ensuring the water just covers the fruit.

Bring the mixture to a gentle simmer, then reduce heat to medium-low to maintain small bubbles without a rolling boil.

Simmer for 8 to 10 minutes, stirring occasionally until the fruit softens and releases its juice.

Pour the cooked fruit mixture through a fine mesh strainer set over a bowl, pressing gently with the back of a spoon to extract all liquid.

Return the strained liquid to the saucepan over medium heat.

Stir in granulated sugar and citric acid powder, stirring constantly until completely dissolved and the mixture becomes clear, about 2 to 3 minutes.

Remove the saucepan from heat and stir in fresh lemon juice until combined.

Allow the cordial to cool to room temperature, about 20 to 30 minutes, before bottling.

Using a funnel, pour the cooled cordial into clean, dry glass bottles with tight-fitting lids and store in a cool, dark place or refrigerate.