Make a simple syrup by combining the sugar and water in a medium-size heavy-bottomed saucepan over medium-high heat. Add the lemon zest and juice and bring to a boil, stirring to dissolve the sugar. Boil for 2 minutes and remove from the heat.
Combine the dried fruits together in a large mixing bowl. Pour the simple syrup over them, toss to coat, and let steep for 5 minutes. Strain and reserve the syrup.
Creme the butter, sugar, and almond paste together in the bowl of an electric mixer fitted with a paddle at low speed, occasionally scraping down the sides of the bowl. Beat until the mixture is fluffy and smooth, about 2 minutes. Add the eggs one at a time, mixing in between each addition on low speed and scraping down the sides of the bowl as necessary. Add 1/2 cup of the Grand Marnier and mix to incorporate.
Combine the flour, baking powder, salt, cinnamon, and nutmeg in a medium-size mixing bowl and blend well. Add this mixture 1/2 cup at a time to the butter mixture with the mixer on low speed, each time mixing until smooth, about 2 minutes. Scrape down the sides of the bowl as necessary. The batter will be thick. Add the warm fruit and all the nuts a little at a time, mixing well. Scrape down the sides of the bowl and the paddle. Preheat the oven to 350 degrees F. Lightly grease twelve 1 pound loaf pans. Spoon about 1 cup of the batter into each pan. Bake until golden and the tops spring back when touched, about 45 minutes (rearranging them after 25 minutes if necessary to brown evenly).
Cool for 10 minutes in the pans. Remove cakes from the pans and cool completely on wire racks. Wrap each cake in a layer of cheesecloth. Store in plastic storage bags until they are slightly stale, 3 to 4 days.
Combine the reserved simple syrup with the remaining 1/2 cup Grand Marnier and the bourbon. Without removing the cheesecloth, make tiny holes with a toothpick randomly on the top of each cake. Pour 2 tablespoons of the syrup over the top of each cake once every 2 to 3 days until all of the syrup is used. Let the cakes age for up to 3 weeks before eating.
Yield: 12 cakes