Line two baking sheets with silicone mats or parchment paper. Set aside.
Sift together almond flour and powdered sugar in a bowl. Discard any large bits remaining.
In a stand mixer bowl, beat egg whites on medium speed until foamy. Add cream of tartar and continue beating until soft peaks form.
Gradually add granulated sugar while beating. Increase speed to high and beat until stiff peaks form.
Add several drops of red gel food coloring and beat to incorporate fully.
Gently fold the sifted almond flour mixture into the meringue in three additions. Continue folding until the batter flows like lava and forms ribbons.
Transfer the batter to a piping bag fitted with a round tip. Pipe 1.5-inch circles onto the prepared baking sheets. Tap trays firmly to release air bubbles, and use a toothpick to pop remaining bubbles.
Allow the macarons to rest at room temperature for 30 to 45 minutes or until the tops are dry to the touch.
Preheat oven to 300°F (150°C). Bake the macarons for 16 to 18 minutes, rotating halfway. Let cool completely on the baking sheet.
To make the buttercream, beat the butter until smooth. Add powdered sugar and beat slowly until combined. Add heavy cream and vanilla extract, then beat until light and fluffy.
Transfer the buttercream to a piping bag and pipe a dollop onto half the macaron shells. Top with remaining shells to form sandwiches.
Melt chocolate chips with vegetable oil using a double boiler or microwave in short bursts, stirring until smooth.
Using a spoon or brush, decorate the center of each macaron with a chocolate belt.
Cut small belt buckles out of gold fondant and attach them to the chocolate belts to complete the Santa look.
Store macarons in an airtight container in the refrigerator for at least 24 hours to mature before serving.