Line 2 large baking sheets with parchment. In a fine-mesh sieve, shake flour and confectioners’ sugar into a large bowl, breaking up any clumps with a fork. Discard solids in sieve (should be no more than 1 Tbsp.).

In the large bowl of a stand mixer fitted with the whisk attachment, beat egg whites and cream of tartar on medium-low speed until frothy, 30 seconds to 1 minute. Increase mixer speed to medium and, with the motor running, slowly add granulated sugar, about 1 Tbsp. at a time, and waiting until dissolved before adding more (this should take 3 to 4 minutes).

Increase speed to medium-high and continue to beat until small stiff peaks form when whisk is removed and flipped point-up, 1 to 2 minutes more (do not overmix).

Remove bowl from stand mixer and sprinkle half of flour mixture over egg white mixture. Using a flexible rubber spatula, fold in flour mixture in smooth, sweeping strokes, working around sides of bowl with an occasional stroke through the middle, until just incorporated. Add food coloring and remaining flour mixture and continue to fold until incorporated and you can draw a complete figure 8 with a ribbon of batter without the batter breaking (do not overmix).

Transfer batter to piping bag fitted with 1/2" round tip. Holding piping bag so tip is 1" above and perpendicular to prepared sheet, pipe 1" circles in rows, spacing 1" apart, as macaron will spread. Using both hands, pick up tray about 2" above work surface and lightly bang against surface twice to expel any air pockets. Repeat with second prepared sheet. Using last bits of batter, glue corners of parchment to baking sheets.

Let rest at room temperature until dry to the touch on top, 15 to 45 minutes, depending on the humidity in the room.

Arrange a rack in center of oven; preheat to 325°. Bake macarons one baking sheet at a time, rotating after 8 minutes, until firm to the touch on top and crisp, 10 to 12 minutes. Let cool.

Arrange half of shells on a clean, dry baking sheet flat side up. Scoop 1/2 tsp. jam onto flat sides, then close with remaining shells rounded side up.