Preheat your oven to 225°F (110°C). This low temperature is essential for slowly drying out the meringue without browning it.

Prepare your baking sheet by lining it with parchment paper or a silicone baking mat. This will prevent the meringue from sticking to the pan.

Separate your egg whites. Crack the eggs and carefully separate the whites from the yolks. You can use an egg separator or simply use your hands to transfer the egg whites from one half of the shell to the other, letting the excess white drip into a bowl.

Beat the egg whites. In the bowl of a stand mixer or in a large mixing bowl using an electric mixer, use the whisk attachment to whisk the egg whites on medium speed until they start to become frothy. This should take about 1 to 2 minutes.

Add the cream of tartar (if using). Cream of tartar is an acidic ingredient that helps stabilize the egg whites and create a stiffer meringue. If you don't have cream of tartar, you can skip this step, but your meringue may not be as stable.

Gradually add the sugar. With the mixer still running, slowly add the sugar to the egg whites, about 1 tablespoon at a time. Continue whisking until the sugar is fully incorporated and the meringue forms stiff peaks. This should take about 5 to 7 minutes.

Add the vanilla extract or other flavoring, if using, once the meringue has formed stiff peaks, and beat for an additional 30 seconds to 1 minute until it’s fully incorporated.

Pipe or spoon the meringue onto the prepared baking sheet. You can use a piping bag fitted with a large star tip to create decorative shapes, or simply spoon the meringue onto the baking sheet in dollops.

Bake the meringue. Place the baking sheet in the preheated oven and bake for 1 hour and 15 minutes to 1 hour and 30 minutes, or until the meringue is dry and crisp on the outside.

Cool the meringue. Once the meringue is done baking, turn off the oven and let the meringue cool completely in the oven with the door closed. This will help prevent the meringue from cracking.

Enjoy your meringue! Once the meringue is completely cool, you can enjoy it on its own or use it as a topping for pies, cakes, or other desserts.