Take the rhubarb and add it to a non-reactive bowl.
Add 3 cups of the strawberries and 2 cups of sugar.
Add the lemon juice and the spent halves of the lemon.
Cover the bowl and let sit in the refrigerator overnight.
The next day roast the other 3 cups of strawberries at 300 degrees for 2 hours.
Add the roasted berries to the rhubarb mixture.
Simmer the mixture in a large saucepan until you reach the gel point test at 20 minutes but it could take up to 40 minutes to gel.
Once the jam has gelled. Place in hot sterilized jars and process in a water bath for 10 minutes.