After making your citrus selection, make sure you wash the fruit with cold water. Then, soak the fruit in a vinegar solution for about 5 minutes (1 part water - 1 part vinegar)
Using a mandoline, slice the fruit as thin as possible. Lay out the citrus wheels on parchment paper covered baking sheet and place in the oven. (we dried some sage with our fruit to give our citrus an herby aroma)
Dry out the citrus until the wheels get crispy. The best temperature to do so will be between 125 and 170 Fahrenheit. Don't try to speed up this process by drying on a higher temperature or the fruit will burn. (this process could take between 6 and 12 hours depending on the fruit you are drying, the thickness of the wheels and the minimum temperature of your oven)
Once crispy, take the wheels out of the oven and let them cool down before granulating them in the blender. (don't let the citrus wheel out of the oven for too long before throwing them in the blender. They might re-moisten, making it impossible to blend into a dust)
Grind the crispy citrus wheels in a blender until you get a fine powder-like texture. (if your dust still feels a little moist, spread it well on the parchment paper and toast it for another 30 minutes or until it gets completely dry)
Vacuum seal the dust, making sure no moisture gets in.