Preheat the oven to 300 degrees F using the convection setting. Line baking sheets with silicone mats.
Measure the confectioners' sugar and almond flour. Place them into a food processor and blend together. Sift the sugar-almond flour mixture, a little at a time, through a fine-mesh sieve into a large bowl, pressing with a rubber spatula to pass through as much as possible. It will take a while, and up to 2 tablespoons of coarse almond flour may be left; just toss it.
On high speed, beat the egg whites in the bowl of a standing mixer using a whisk attachment. When the egg whites reach soft peak stage turn machine to low and add sugar. Turn mixer to medium speed and mix approximately 10 mins or until the whipped egg whites appear shiny and the sugar is dissolved.
Transfer the beaten egg whites to the bowl with the almond flour mixture. Draw a rubber spatula halfway through the mixture and fold until incorporated, giving the bowl a quarter turn with each fold.
Add the food coloring and extract. Continue folding and turning, scraping down the bowl, until the batter is smooth and falls off the spatula in a thin flat ribbon, 2 to 3 minutes.
Transfer the batter to a pastry bag fitted with a Wilton #12 round tip. Holding the bag vertically and close to the baking sheet, pipe 1 1/4-inch circles. Firmly tap the baking sheets twice against the counter to release any air bubbles.
Let the cookies sit at room temperature until the tops are no longer sticky to the touch, 15 minutes to 1 hour, depending on the humidity.
Bake the first batch until the tops of the macaroons are crusty and shiny and rise to form a "foot," about 12 minutes. Transfer to a rack to cool completely. Peel the cookies off the mats and sandwich with a thin layer of filling.
To Make Eggnog Filling
Beat all the ingredients on HIGH speed in the bowl of a standing mixer using a whisk attachment until the color of the cream turns from shiny to dull.
To Assemble the Eggnog French Macarons
Make it like the sandwich with the eggnog filling.
Assemble the French Macaron
Make it like a sandwich with the eggnog filling
Notes
Variation idea: you can use the macaron cookie like the fruit tart. Use the start piping tip to pipe eggnog filling on top. Sprinkle pomegranate on top. Shave some dark chocolate on top if you feel like it!