Put egg whites in a mixing bowl and set aside to come to room temperature.
Measure the almond flour, powdered sugar, and salt into the bowl of a food processor. Process the mixture finely, then sift, discard any large bits.
Using a kitchen scale to measure accurately, divide the mixture equally between two small bowls, and set aside.
Measure the granulated sugar in a small bowl.
Add the cream of tartar to the whites, and mix on medium-high speed, using the whip attachment.
When the whites hold soft peaks, start adding the granulated sugar, one tablespoon at a time.
When all the granulated sugar has been incorporated, continue to whip until stiff peaks form.
Using a kitchen scale to measure accurately, divide the meringue equally between two medium mixing bowls.
Tint one bowl of meringue with red gel paste food coloring until desired tint, and the other with blue gel paste food coloring until desired tint.
Sift half the almond flour mixture on top the the blue meringue, and fold together until the batter drops from the spatula in a long ribbon.
Transfer to a piping bag fitted with a large round tip, and pipe 1 1/2-inch diameter rounds onto parchment-lined baking sheets.
Repeat with the red meringue.
Sprinkle edible star glitter on the tops of the freshly piped red macarons.
Allow to dry for 60 minutes, until the tops of the macarons are dry to the touch.
Preheat the oven to 300 degrees F, and bake the macarons, one sheet at a time, until set, about 10-12 minutes. Do not let brown or over cook!
Allow to cool on the baking sheet, then carefully peel from the parchment and place upside down.
