Lemon Pannacotta with Lemon Marmalade

Using a knife, cut peel and white pith, end to end, from lemons. Juice enough flesh to measure 1/3 cup; reserve. Bring a large saucepan of water to a boil. Add peel; boil for 5 minutes. Drain; repeat 2 more times. Let peel cool; slice lengthwise into thin strips, then crosswise in half. In a small heavy saucepan over medium heat, stir sugar, reserved 1/3 cup lemon juice, and 1/4 cup water until sugar dissolves. Add peel, bring to a simmer, and cook until mixture is reduced to 2/3 cup and an instant-read thermometer reads 225 °F about 10 minutes. DO AHEAD: Can be made up to 2 weeks ahead. Cover and chill.