In a large skillet, combine raspberries, sugar, lemon juice, and a pinch of salt. Cook over high, stirring, until sugar dissolves and mixture boils. Reduce to a rapid simmer and cook, stirring occasionally, until mixture thickens, 12 to 15 minutes. Transfer 3/4 cup jam to an airtight container.

Bring raspberries to a boil in a very large pot. Cook for 4 minutes. Add sugar and lemon juice; stir well. Bring back to a boil, stirring constantly. Cook for another 4 minutes. Remove pot from heat and pour jam into sterilized jars, leaving 1/4-inch of space at the top. Seal and transfer jars into a boiling water bath.