4egg whitesroom temperature (or 1/2 cup liquid egg whites)
½teaspooncream of tartar
Preheat oven to 225°F/107°C and place rack in center of oven.
Wipe mixing bowl and whisk with a towel lightly dampened in white vinegar to ensure they're completely grease free.
Add egg whites to bowl and whisk on medium speed until frothy.
Add cream of tartar and continue to whisk until soft peaks form.
Increase speed to medium-high and add sugar. Continue beating until stiff peaks form.
Add vanilla extract and food coloring, if using.
Plop by spoonful or pipe quarter-sized cookies using an icing bag onto lightly greased baking sheets about 1 inch apart.
Bake both sheets at the same time for 90 minutes then turn the oven off. Do NOT open the oven door. Let the meringue cookies stay in the oven for at least one hour, up to overnight, until completely cooled.
Store in an air-tight container for up to 2 weeks. To freeze, place a sheet of parchment paper between layers in an airtight container. Defrost layers separately on the counter for 1 hour.