In small skillet, heat sugar over medium, stirring often, until color turns amber, about 6 minutes. Divide among six 8-oz. ramekins. In bowl, whisk condensed milk, evaporated milk, eggs, and peanut butter; pour into ramekins. Place ramekins in roasting pan. Fill pan halfway with hot water. Bake at 350° until flan is almost set in center, about 30 minutes. Refrigerate flan until set, about 4 hours. Unmold flan. Top with jelly, nuts, and salt.