Unsalted butter, for greasing the dish
1 large panettone (about 2 pounds)
1 1/2 cups cherry jam
8 ounces cream cheese, at room temperature
3 1/2 cups half-and-half
6 large eggs
1/4 cup granulated sugar
1 teaspoon pure vanilla extract
1/2 teaspoon ground cinnamon
1/4 teaspoon kosher salt
1/2 cup blanched sliced almonds
Confectioners' sugar, for dusting