Preheat oven to 350°F Fill kettle or covered 4-quart saucepan with water; heat to boiling over high heat.
Meanwhile, from orange, with vegetable peeler, remove 6 strips peel, about 3" by 1" each. With knife, trim off as much white pith as possible from peel. In 1-quart saucepan, heat orange peel, 3/4 cup sugar, and 1/4 cup water to boiling over medium heat; cover and cook 5 minutes. Remove cover and cook 1 to 2 minutes longer or until sugar mixture is amber in color. Pour hot caramel into 9" by 5" metal loaf pan. With fork, remove and discard orange peel. (Hold loaf pan with pot holders to protect hands from heat of caramel.) Set pan aside.
In large bowl, with mixer on medium speed, beat cream cheese and remaining 1/2 cup sugar 2 minutes, occasionally scraping bowl with rubber spatula. Beat in pumpkin, then eggs, 1 at a time. Reduce speed to low; beat in evaporated milk, cream, liqueur, vanilla, cinnamon, nutmeg, and pinch salt just until well mixed.
Pour pumpkin mixture through medium-mesh sieve over caramel in loaf pan, pressing it through with rubber spatula. Place loaf pan in 13" by 9" baking pan; place in oven. Carefully pour boiling water into baking pan to come three-quarters up sides of loaf pan.
Bake 1 hour and 10 to 15 minutes or until knife inserted 1 inch from edge of custard comes out clean (center will jiggle). Remove loaf pan from baking pan to cool on wire rack 1 hour. Cover and refrigerate cr?me caramel at least 8 hours or overnight.
To unmold, run small metal spatula or knife around sides of loaf pan; invert cr?me caramel onto serving plate. Leave loaf pan in place several minutes, allowing caramel syrup to drip from pan onto loaf. (Don't worry if some caramel remains in loaf pan.).
Do ahead: Bake dessert up to 2 days ahead. Leave in loaf pan for easy transporting, and unmold at your destination. Since the shape of the dessert is unusual and there is a lot of caramel sauce, don't forget to bring a deep rectangular platter with you.