Place rack in center of oven. Mist a 9-by-13-inch baking dish with cooking spray. Arrange bread in pan. In a saucepan, mix 1 cup sugar with 2 cups water. Bring to a boil over medium-high heat. Add cranberries and cook, stirring, until berries have popped, 5 minutes. Strain cranberries, reserving syrup, and place berries in a bowl. Stir 1/4 cup sugar into hot berries.
In a separate pan, mix cream, milk and salt. Cook over medium heat until hot, 5 minutes. Let cool slightly. With electric mixer, beat eggs, 3/4 cup sugar and vanilla until mixture is pale yellow, 3 minutes. Gradually whisk in warm cream mixture.
Pour mixture through a strainer set over bread, distributing evenly. Spoon cranberries on top. Let stand at room temperature for 30 minutes. Preheat oven to 350°F.
Place baking dish in a roasting pan; pour boiling water into roasting pan until it reaches halfway up baking dish. Bake until just set and custard no longer wiggles in center, 40 minutes. Let cool for 15 minutes before serving. Rewarm syrup and serve with bread pudding.