Prepare your jars, lids & rings by washing and drying them.
Place the strawberries, sugar and lemon juice in a pot.
Cook the strawberries on medium high heat, and mash as the strawberries are cooking. This will break them up and make them more into a sauce consistency.
Optional: As the strawberries are cooking, add the butter to prevent foaming.
If water bath canning the strawberry sauce, fill your canner with enough water to cover the tops of the pint jars. Put the canner on your stove on high heat, to start boiling your water.
Scrape off the foam from the strawberry sauce cooking, if any.
Ladle the hot strawberry sauce into the pint jars, leaving 1 inch of headspace. Wipe the jar rims clean before adding the lids and rings.
Storing for immediate use: Let the strawberry sauce cool in the jars for 1 hour before placing them in the refrigerator to use as desired.
Water Bathing: Place jars in the canner basket, and slowly lower the jars into the boiling water. Make sure the water comes back to a rolling boil before letting the strawberry sauce jars process for 15 minutes.
After processing in the water bath, turn the stove off, remove the lid, and let the jars sit in the water another 5 minutes before removing.
Let the jars sit on your counter for about 12 hours before checking that the jars sealed properly. If the jars sealed properly, store in a cool place for up to a year. If the jars did not seal, place in your refrigerator to use strawberry sauce earlier.