Combine the water, sugar and salt in a sauce pan and heat just until the sugar and salt dissolve. Allow to cool to room temperature.
Place the pork roast in a plastic gallon zipper top bag or a sealable container and fill with the brine. If using a plastic bag, I suggest double bagging it in and placing it in a baking dish or bowl in the refrigerator to prevent the bag from being punctured. Place in the refrigerator and allow to sit overnight or up to 24 hours.
Cooking the Pork Roast:
Remove the roast from the refrigerator and allow to sit at room temperature for 30 minutes. Preheat oven to 450 degrees.
Remove the roast from the brine (and discard the brine) and allow liquid to drain from the roast. Place the roast on a rack in a baking pan. Place in the oven and cook at 450 for 15 minutes.
Lower the temperature to 300 degrees and cook the roast until the internal thermometer inserted into the middle of the roast registers 145 degree (40-50 minutes). Check the temperature at 40 minutes and then every 5 minutes so the roast does not overcook.
Remove the roast and tent the pan with tin foil (shiny side in) for an additional 15 minutes which allows the temperature to rise an additional 10 degrees still allowing the roast to stay moist and succulent.
Instructions for Rhubarb-Cherry Port sauce:
In a medium saucepan, heat the oil over medium-high heat. When the oil is shimmering add the shallots and sauté until the shallots become limp; 2-3 minutes.
Add the cherries, rhubarb, sugar, water, and port to the saucepan. Bring the mixture to a low boil, then lower the heat until the mixture is simmering. Cover and allow to cook 5-10 minutes until the rhubarb has softened.
Remove from heat and add the cardamom and vinegar. Spoon into a free standing blender, or use an immersion blender in the sauce pan, to blend the mixture into a smooth sauce.