About the only big pie/cake--->holiday things are pumpkin pie for Thanksgiving and Birthday Cake. Fruitcake is totally a Xmas thing its just had a bad rap in recent years so maybe it wouldn't count. The default Xmas pie is Pecan, but neither Fruitcake or pecan pie hold any really really major significance the way BBQ does to 4th of July or Turkey and Pumpkin Pie hold to Thanksgiving. The closest would probably be cookies, especially gingerbread, but shaped cookies covered in frosting and sprinkles plus eggnog or hot chocolate with a candy cane in it are generally what best qualify as things that would specifically tend to summon Christmas to mind. Everything else would tend to be family, ethnic, or region specific, especially the first one.