Heat a medium saucepan over medium heat. Add 2 tablespoons butter, and melt. Whisk in flour, and allow to cook for 1 minute.
In a medium bowl stir together ginger ale, soy sauce, garlic powder, onion powder, and lemon juice. Slowly pour ginger ale mixture into the roux, whisking constantly. Keep whisking to remove any lumps. (Start your medallions now and everything will finish around the same time.)
Cook for 5 to 10 minutes, whisking often until sauce thickens. Season with salt and pepper to taste, if desired. Keep warm of low heat until ready to serve, stirring occasionally.
Pork Medallions:
Heat a large skillet over medium to medium-high heat. Add 1 tablespoon butter and melt.
Cut your pork tenderloin into 1/2-inch medallions. (I got about 10 pieces from our tenderloin.) Lay the medallions flat on the cutting board and season with salt and pepper to taste.
Place as many medallions as will fit in your skillet, seasoned side down into the hot skillet, and cook for 3 to 4 minutes on each side, or until the meat turns white halfway up the sides. Turn only once. Remove cooked medallions to a plate and cover loosely with foil while you cook the rest of the medallions.
Pour sauce over cooked medallions for serving.
Notes
Make the roast version: Double the sauce ingredients and pour them into a 9" x 13" glass baking dish. (also, sub 4 fresh, minced garlic cloves for the garlic powder.) Add a 4 pound pork loin roast to the dish. Cover and refrigerate at least 7 hours, or overnight, turning once. Preheat oven to 350 degrees F. Cook roast in the marinade for 1 ½ to 2 hours, or until digital thermometer reads an internal temperature 155 degrees F when inserted into the center of the roast. Remove roast from pan, wrap in foil and let stand 10 minutes. Use 3 cups of the pan juices to make the sauce - with 3 tablespoons butter and 1/4 cup flour for the roux.