Preheat the oven to 375°F and add the pistachios to a baking sheet.
Roast the Pistachios. Roast the pistachios in the preheated 375°F oven just long enough to bring the oils to the surface -- about 7 minutes. They will be aromatic and might look a bit wet when they're ready. (Do this even if the pistachios you buy say they've been roasted.)
Grind the pistachios. Once they've cooled to room temperature, add the roasted pistachios to a food processor fitted with the blade attachment. Blend for about 7 minutes. Add the sugar and salt and blend for another couple of seconds.
Cool. Let it cool down before refrigerating. (It should last at least a month in a tightly sealed container in the refrigerator.)