In a large saucepan, combine the raspberries and lemon juice. Crush the raspberries with a wooden spoon to release their juices.

Add the sugar and pectin to the saucepan. Stir well to combine and bring the mixture to a boil over medium heat.

Once boiling, continue to cook for 10-15 minutes, stirring frequently, until the jam thickens.

Remove the saucepan from heat and skim off any foam. Pour the hot jam into sterilized jars using a canning funnel, leaving about 1/4 inch headspace.

Seal the jars with lids and process in a boiling water bath for 5-10 minutes to ensure they are sealed properly.

Allow the jars to cool completely at room temperature. Store in a cool, dark place.