Prepare the panettone: Cut 1/2 inch off the bottom of the panettone. Reserve. Hollow out the panettone, leaving a 1 1/2-inch border around the bottom of the cake and 1 inch toward the top. Scoop out the insides. Add half of the pistachio ice cream. Layer in cherries, and finish with the remaining pistachio ice cream. Replace the bottom and put the panettone in the freezer to set.
Make the meringue: In a small saucepan, combine 1 1/2 cups sugar, cream of tartar and water. Bring to a boil, then reduce heat to medium and cook without stirring for 4 minutes until the combination reaches 240 degrees.
In the bowl of a stand mixer, whip egg whites to soft peaks, starting at low speed and gradually increasing speed to high, then slowly sprinkle in remaining sugar. Once combined, mix for 30 seconds more, and then slowly pour in sugar syrup. Beat for 5 to 8 minutes at high speed until the bowl of the stand mixer has cooled to the touch.
Assemble the baked Alaska: Remove the cake from the freezer and place on a cake stand. Spread the meringue over the top and sides of the cake, creating a dome shape. The baked Alaska should resemble a small mountain with pillowy swirls of meringue. Finish the cake by toasting the meringue with a torch to a golden color. Serve immediately. Cake is best eaten the day of.
