Using a permanent marker, draw 1 1⁄2-inch circles 1 inch apart on 3 sheets of parchment paper. Turn parchment upside down on 3 large rimmed baking sheets.

In the work bowl of a food processor, pulse almond flour and confectioners’ sugar until finely ground and fully combined. Transfer to a large bowl. Add 3 large egg whites (90 grams); fold until combined.

In a small saucepan, stir together granulated sugar and 1⁄3 cup (80 grams) water. Cook over high heat, without stirring, until an instant-read thermometer registers 240°F (116°C) to 245°F (118°C).

Meanwhile, in the bowl of a stand mixer fitted with the whisk attachment, beat remaining 3 egg whites (90 grams) at low speed until foamy. Increase mixer speed to medium-high, and beat until medium-stiff peaks form. (Egg whites and sugar syrup should be prepared so they are ready at the same time.)

With mixer on high speed, add sugar syrup to egg whites, carefully pouring straight into egg whites, avoiding side of bowl and whisk. Beat until mixture is cooled and stiff peaks form, 4 to 5 minutes.

Add one-fourth of meringue (about 1 cup or 85 grams) to almond flour mixture; stir vigorously until combined. Add remaining meringue, and carefully fold until mixture is ribbon-consistency. (Mixture should be thick and slowly but freely fall off the spatula in a “V” shape; when you drag the spatula through the batter, it should move like lava and slowly come back together.)

Transfer batter to a pastry bag fitted with a medium round tip (Ateco #804). Holding piping tip perpendicular to pan, pipe batter within drawn circles on prepared pans, applying pressure and leaving tip stationary until batter just reaches drawn circle. Move and lift piping tip in a quick circular motion as you finish piping each macaron shell to prevent a point from forming on top. Slam pans vigorously on counter 5 to 7 times to release air bubbles. Top with nonpareils as desired. Let stand at room temperature until a skin forms on top of macaron shells, 45 minutes to 1 hour. (Batter should feel dry to the touch and should not stick to your finger.)

Preheat oven to 300°F (150°C).

Bake until shells are firm but have a slight wobble to the touch, 15 to 18 minutes. Let cool completely on pans.

Spoon Almond Swiss Meringue Buttercream into a pastry bag fitted with a medium round piping tip (Ateco #806.) Pipe a border of buttercream onto flat side of half of macaron shells. Fill each center with about 1⁄2 teaspoon (3 grams) jam. Lightly press remaining macaron shells, flat side down, on top of buttercream and jam. Refrigerate in an airtight container for up to 3 days.