Special equipment: a candy thermometer; 3 silicone mats or parchment paper; a pastry bag fitted with a 1/4-inch round tip
Preheat the oven to 300 degrees F and place an oven rack in the middle position. Line 3 baking sheets with silicone baking mats or parchment paper. (If you are using parchment paper, use a pencil to trace 1 1/2-inch circles spaced 1 inch apart to help guide you when piping the batter.)
For the Italian meringue: Heat the sugar and water in a small pot over medium heat until a candy thermometer registers 235 degrees F ("soft-ball stage").
Meanwhile, using an electric mixer, whisk the egg white in a clean, grease-free bowl until white and frothy. With the mixer on medium speed, pour in the sugar syrup in a slow, steady stream. Increase the speed to high and whisk until a stiff and glossy meringue forms, about 10 minutes. Add the food coloring and whisk until incorporated, about 1 minute more.
For the batter: Sift the almond powder and confectioners' sugar into a large bowl. Using a rubber spatula, stir in the egg white until evenly combined. Gently fold half of the meringue into the batter. Once incorporated, fold in the remaining half of the meringue until well combined.
Transfer the batter to a pastry bag fitted with a 1/4-inch round tip. Pipe 1 1/2-inch circles of batter onto the baking sheets, spacing them about 1 inch apart. The batter should yield approximately 50 cookies. Tap the sheets to allow any air bubbles to escape. Let the meringues sit at room temperature until the tops are no longer sticky to the touch, 15 to 30 minutes.
Bake, one sheet at a time, for about 15 minutes. Place the sheets on wire racks to cool.
Once the cookies are completely cool, peel them off the mat. Spread raspberry jam on the flat side of half of the cookies and top with the remaining half of the cookies. Store the macarons in the fridge, covered in plastic, until ready to serve.
Flavor combinations for these cookies are endless--I have even tasted savory macarons flavored with Parmesan cheese. You can substitute the coloring for anything you like and also the filling to match. One of my favorites is a caramel macaron filled with some salted butter caramel. It's worth a try!