Preheat oven to 225 degrees F.
Line two baking sheets with parchment paper and set aside.
Place egg whites into a mixing bowl or the bowl of your stand mixer. (NOTE: It's important to have your egg whites at room temperature. This gives them as much lift as possible!)
Beat whites at medium speed until white and frothy.
Add cream of tartar and salt, then continue to beat the mixture until soft peaks form.
Once you've reached soft peaks, add sugar slowly (a few teaspoons at a time - don't rush it) until all the sugar has been added, it's completely dissolved and stiff peaks have formed.
Add in the food coloring (if you're using it) and then quickly put the meringue into a large piping bag.
Pipe heart shapes or create little meringue buttons on to the prepared baking sheets. If you don't want hearts or buttons, be bold and daring and create any shapes that make you smile!
Bake for 45 minutes and then turn OFF your oven. Don't open the door, (turn on the oven light if you must peek at them!) then just let the cookies hang out in the oven for an hour or two to cool and get crispy on the outside.