Add the butter and sweetener to a medium saucepan. Heat on medium until melted. Add the pecans and cook for about 5-8 minutes until the syrup begins turning brown and the pecans smell toasted. Remove from the heat. Stir every 5 minutes as they cool. The syrup will continue to thicken. Once they are well coated and room temperature transfer to a waxed paper lined baking sheet. Refrigerate until the coating is hard.