Remove the pie crusts from the refrigerator and let sit on the counter for 15 minutes.
Gently roll out 1 pie crust. Using a round cookie cutter that is a bit larger than the mini muffin tin circles, cut the pie crust into as many circles as you can. Carefully place the cutouts into the mini muffin tin. Push down in the middle of the cutouts with your fingers and shape the crust to the shape of the pan.
Place in the oven and bake per package directions, or until lightly golden brown. Once done baking, remove from the oven and place the mini bites on a wire rack to completely cool.
Repeat steps to bake the second batch.
Once the mini pie crusts are cooled fill each crust to the top with store bought lemon curd. Set aside.
In the bowl of a stand mixer, add room-temperature egg whites. Use the whisk attachment to beat on medium-high until they become frothy and soft peaks form. This takes around one minute.
While the mixer is still running add the cream of tartar, then begin adding the sugar a tablespoon at a time, while continuing to beat on high. Go slowly when adding the sugar; this part may take 5 to 10 minutes of continuous beating/adding sugar. Make sure to scrape the sides of the bowl to get all sugar incorporated.
When the mixture has formed stiff peaks stop the stand mixture. Over-mixing will cause your meringue to fall.
Add meringue to a piping back with a tip ¾ of the way full. Pipe the meringue on the top of each lemon curd bite.
Preheat the oven broiler too high. Place the mini-muffin pan under the broiler until the meringue is evenly toasted, about 2 minutes. Watch it carefully so it doesn't burn.
This recipe can also be made as one large 9-inch pie instead of as tarts.
Spooning the lemon curd into a Ziploc bag with the corner snipped off and piping it into the shells makes it much easier than trying to spoon the filling in.
It is very important that your egg whites are at room temperature. They whip faster than cold egg whites and they also whip to a greater volume than cold egg whites.
Cream of tartar helps to stabilize the meringue making it bigger and fluffier.
Stiff peaks stand up when the beaters are lifted.
If you have a kitchen torch, you could also use that to brown the meringue instead of under the broiler.