For the raspberry jelly with lemon balm, carefully select raspberries and place in a saucepan. Bring to a boil with 500 ml of water and cook over medium heat for 10 minutes.
Place a colander on a saucepan, spread with a wet muslin cloth and carefully pour in the raspberries. Let drain for at least 2 hours
Place the prepared jars (twist-off or jars with rubber ring and swing-top) on a damp kitchen towel. Squeeze the lemon and set the juice aside. Rinse and dry the lemon balm. Place 2-3 stems at a time in a jar.
Bring raspberry juice to a boil with preserving sugar and juice of one lemon, stirring. Boil for 3 minutes, skimming a few times.
Pour the hot jelly into the prepared jars up to the rim, seal and turn upside down. After 30 minutes, turn repeatedly to the other side.