Before starting, make sure your Cooked Ham (1) has been out of the fridge for at least 2-3 hours to come to room temperature.
Preheat oven to 325 degrees F (162 degrees C). Adjust oven rack to the lowest position. Pour Ginger Ale (24 fluid ounce) into the bottom of the roasting pan. Place slices of Onion (1) in the bottom of the pan and insert roasting rack.
In a medium saucepan, whisk together the Brown Sugar (1 cup), Apricot Preserves (1 cup), Raspberry Preserves (1/2 cup) and Dijon Mustard (1/3 cup). Bring to a low simmer and reduce heat to low, stirring often until sugar is dissolved and preserves melted; set aside.
Roll out 2 large pieces of foil to wrap your ham in, making sure they overlap in the center. Remove ham from packaging and remove any plastic or paper disk over the ham bone. Place ham on foil, and brush entire ham with approximately 1/3 of the warm glaze, including in between each slice. Tightly wrap ham with foil and place ham flat/face side down on the roasting rack (or on top of onion slices on bottom of roasting pan if you don’t have a roasting rack).
Bake ham for about 90 minutes (allow 10 minutes per pound) or until the center registers 125 degrees F (50 degrees C). This temperature is safe because we are simply warming a fully-baked ham. Better to “underbake” than “overbake” – you don’t want to overcook your spiral ham or it will be dry.
Near end of baking time, re-warm glaze over low heat.
Remove ham from oven; carefully unwrap ham and discard foil. Spoon juices from the bottom of the roasting pan over the top of the ham. Brush the top and between slices of the ham with half of the remaining glaze.
Cover loosely with foil and return to oven; continue baking for an additional 20 minutes.
Remove from oven and tent with foil. Let ham rest for 15 minutes before removing from pan and serving.
Add 1/2 cup of hot glaze from pan to remaining Glaze and serve warm on the side to pour over ham slices, or serve with spicy Dijon mustard.