Dice mushrooms and add to stock pot. Add salt and lemon juice. Cook, stirring often for around 5 minutes till mushrooms start to release their liquid.
Cover the pot and reduce heat to low simmer for 10 minutes stirring occasionally. The mushrooms will be very soft and the mixture will be very wet.
Uncover and increase to medium heat for minutes or until the liquid is almost evaporated. Stir in lemon zest, thyme, pepper and vinegar. Bring to a boil stirring constantly, for 1 minute.
Ladle hot tapenade into hot jars, leaving 1/2 " headspace.
When filling the jars be sure there is enough liquid on top of the tapenade to cover the solids. Processing in a water bath for 15 minutes.
Yields 5 - 1/4 pints
Great on baguette slices for quick canapes or with grilled steak or on a burger!