In a large saucepan, combine strawberries, sugar, lemon juice, and zest (if using).

Cook over medium heat, stirring often, until sugar dissolves and mixture begins to bubble.

Use a potato masher or spoon to mash the strawberries to your desired consistency.

Continue to simmer the jam, stirring frequently, for 20–30 minutes, or until thickened and reduced.

To test the jam, place a small spoonful on a chilled plate — if it wrinkles when pushed, it’s ready.

Remove from heat and let cool slightly.

Transfer to sterilized jars and refrigerate for up to 3 weeks, or process in a water bath for longer storage.