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. Remove the strips of lemon zest and discard the zest. Set syrup aside.
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.
Cream the butter, sugar, and almond paste together in the bowl of an electric mixer fitted with a paddle attachment 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, 1 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 orange liqueur 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 12 mini disposable loaf pans (about 3 1/2 inches by 5 3/4 inches). Divide the batter evenly between the pans, about 1 cup each. Bake until golden and the tops spring back when touched, 35 to 40 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. Wrap cakes well in a decorative manner if giving as gifts.
Serve the cakes with the Whiskey Sauce.
Combine 2 1/4 cups of the cream with the bourbon and sugar in a medium-size nonstick saucepan over medium heat. Stir to dissolve the sugar.
In a small bowl, dissolve the cornstarch in the remaining 1/4 cup cream. Add this to the cream-and-bourbon mixture and simmer, stirring often, until the mixture thickens, 4 to 5 minutes. Remove from the heat and serve warm with the fruitcake.
The sauce may be stored, after it has cooled, in an airtight container for 24 hours. When ready to serve, warm over low heat.