Wash and hull the strawberries. Slice into halves or quarters.

If using lemon peel, finely grate it. Combine strawberries, sugar, lemon juice, and lemon peel (if using) in a large saucepan.

Let the mixture stand for at least 30 minutes to macerate. Stir occasionally.

Bring the mixture to a rolling boil over medium-high heat, stirring constantly. Reduce heat to medium-low and simmer, stirring frequently, until the jam reaches setting point (see note below).

To test for setting point, use the wrinkle test: place a small spoonful on a chilled plate. Let cool slightly, then push the jam with your finger. If the surface wrinkles, it's ready. Alternatively, use a jam thermometer; it should reach 220°F (104°C).

Remove from heat. If canning, carefully ladle hot jam into sterilized jars, leaving 1/4 inch headspace. Wipe rims, seal, and process according to your preferred canning method.

If not canning, let cool completely before transferring to sterilized jars or containers. Refrigerate for up to 3 weeks.