Combine the pomegranate juice, sugar and lemon juice in a large saucepan and heat over medium-high heat until the sugar dissolves completely. Be sure to stir while this is taking place.
When the sugar is dissolved, bring the juice to a simmer and reduce the heat enough to maintain a low simmer. Let the syrup cook down for about an hour until it reaches a syrupy consistency. If you measure it out in a measuring cup, you would probably end up with about 1¼ to 1½ cups of pomegranate molasses but who's going to measure it out?
Remove the pan from the heat and let it cool down for 20 minutes. Pour the molasses into a glass jar and let it cool down completely before putting the lid on and storing in the refrigerator.
It should last in the refrigerator for months but I hope you use it up before then on some grilled fish or chicken. It's really that good!