Preheat oven to 200 degrees F. Place egg whites and sugar in a heat-proof bowl that fits over an electric stand mixer, and set the bowl over a pot of simmering water (bain-marie).

Whisk mixture constantly until the sugar dissolves and the mixture is warm to the touch, about 3 minutes. Mix in the salt and cream of tartar.

Transfer the bowl to an electric stand mixer. Add in the strawberry extract and whip the mixture on medium-high speed until stiff, glossy peaks form and the mixture has nearly cooled, about 7 minutes.

Meanwhile, using a small paintbrush, paint 3 vertical stripes of the gel food coloring (spaced fairly evenly apart) along the inside of a large pastry bag fitted with a 0.5-inch round tip.

Fill the pastry bag with the meringue mixture (being careful not to smudge the coloring with the spatula while filling) and pipe 1.75-inch circles onto a silicone baking mat or parchment paper-lined baking sheets, spacing them 2 inches apart.

Bake in the preheated oven for 1 hour and 15 minutes, until the meringues are dry to the touch, crisp on the outside and tender and soft on the inside (if you live in a humid climate or prefer them drier throughout, you may bake them up to 20 minutes longer). Allow to cool completely and transfer to an airtight container.