Cook Strawberries: Add the strawberries, sugar, and lemon juice to a saucepan.
Simmer: Cook on mediumhigh heat, stirring occasionally. When the mixture starts to boil, reduce heat to mediumlow.
Thicken Jam: Continue cooking until the jam is dark and thick, around 200220°F on a thermometer. If you don’t have a thermometer, cook until it’s dark and thick.
Cool: Transfer the jam to a bowl, cover with plastic wrap directly on the surface, and let it cool. Refrigerate for a few hours before using.