https://www.jeffreymorgenthaler.com/how-to-make-your-own-grenadine/
2 cups fresh pomegranate juice (approximately two large pomegranates) or POM Wonderful 100% pomegranate juice
2 cups unbleached sugar
2 oz pomegranate molasses
1 tsp orange blossom water
Method
Heat juice slightly, just enough to allow other ingredients to dissolve easily.
Stir in remaining ingredients, allow to cool, and bottle.
Some recipes are going to tell you you need to remove each individual seed from the pomegranate (a long, painful and finger-stainingly messy process) and either simmer them in water over heat or steep them in water overnight to extract the juice. I’ll tell you what, you want to extract the juice from a pomegranate? Do what I do: cut that puppy open like a grapefruit and press it with your juicer. Done and done. And the resulting juice is far more intense and flavorful than anything you’re going to get from those other methods that employ a bunch of water, believe me.