In a bowl, whisk the sugar, pectin, and salt to combine. If a seedless jam is desired, purée the berries in a blender and strain through a fine-meshed sieve. Otherwise, leave them whole, or cut large ones into quarters.
In a medium saucepan, combine the sherry vinegar, rice wine vinegar, coriander, and cardamom. Bring to a boil over medium heat, and immediately remove from heat. Remove and discard the coriander seeds and cardamom.
Return the saucepan to medium heat and add the sugar mixture, stirring with a wooden spoon until blended; it will be dry at first. Add the strawberries or strawberry purée, and continue to stir, crushing the berries with the spoon, until the mixture is liquefied and comes to a boil. Continue to boil, stirring constantly, until thickened, about 3 minutes.
Pour the jam into a heat-proof bowl and let cool completely. Store it, covered, in the refrigerator. The jam can also be frozen for up to six months.