Pre-heat oven at 250ºF (120ºC).

Clean your bowl and whisk with a paper towel soaked in vinegar. This will remove any grease they may have.

Place the egg whites and cream of tartar or lemon juice in your bowl and whisk at high speed until stiff peaks form.

Now, start adding the white sugar one tablespoon at a time while you're still whisking. Once it's incorporated, touch the mixture with your fingers to see if you feel any sugar granules. If so, keep whisking until the mixture is smooth and shiny. Now, add the vanilla extract and mix until it's well incorporated.

Cover a cookie sheet with parchment paper. Place a small amount of the meringue on the underside of each corner of the parchment paper to anchor it to the cookie sheet. Using a couple of spoons or a pastry bag, shape the meringues on the parchment paper.

Bake for 1½ hour. Then, turn off your oven and leave the door cracked open to let the meringues dry and cool down for a few hours before serving. They can be stored in an airtight container.