Remove lemon rind from the saucepan. Place saucepan over medium to high heat and bring to a boil, before lowering the temperature. Allow your jam to simmer, stirring regularly until the fruit breaks down completely - approximately 15 minutes. Jam should be at 104-105ºC. Alternatively, test to see if your jam is ready by spooning a small amount on to a chilled plate. To test if your jam is ready, put a blob on a chilled plate and run your finger through the middle. If the line remains and doesn't fill in, it's ready.