Wash apricots under cold running water; drain. To peel apricots, blanch in boiling water 30-60 seconds. Immediately transfer to cold water. Cut off peel, cut apricot in half lengthwise and remove pits and fibrous flesh. Combine apricots and water in a large stainless steel saucepan. Bring to a boil over medium-high heat. Reduce heat and boil gently, stirring occasionally, until apricots are soft, about 20 minutes.

Prepare boiling water canner. Heat jars in simmering water until ready to use, do not boil. Wash lids in warm soapy water and set aside with bands.

Transfer apricot mixture to a food mill or a food processor fitted with a metal blade, working in batches, and purée just until a uniform texture is achieved. Do not liquefy. Measure 6 cups of apricot purée.

Combine apricot purée and sugar in a clean large stainless steel saucepan. Stir until sugar dissolves. Bring to a boil over medium-high heat, stirring frequently. Reduce heat and boil gently, stirring frequently, until mixture thickens and holds its shape on a spoon. Stir in lemon juice.

Ladle hot butter into a hot jar leaving a 1/4 inch headspace. Remove air bubbles. Wipe jar rim. Center lid on jar and apply band, adjust to fingertip tight. Place jar in boiling-water canner. Repeat until all jars are filled.

Water must cover jars by 1 inch. Adjust heat to medium-high, cover canner, and bring water to a rolling boil. Process half-pint jars 10 minutes, adjusting for altitude. Turn off heat and remove cover. Let jars cool 5 minutes. Remove jars from canner; do not retighten bands if loose. Cool 12-24 hours. Check lids for seal, they should not flex when center is pressed.