Get ready: Preheat your oven to 250 degrees.
Line a baking (cookie) sheet with parchment paper. Optionally, use a large round cookie cutter to trace 6 circles on the parchment paper, about 3" in diameter. Flip the paper over, marking side down, on the baking sheet, set aside.
Fit your electric mixer or stand mixer with the whisk attachment. Remove eggs from fridge, separate out the whites, and allow to warm to room temp (about 5 minutes).
In your mixer bowl, beat egg whites together with salt until glossy peaks form.
Slowly add in the sugar, and continue whipping until stiff peaks form. Turn off mixer, remove bowl.
Sprinkle vinegar, cornstarch, and vanilla extract over meringue, gently fold in till combined.
Divide the meringue evenly between the circles. Use the back of a spoon to swirl each meringue pile into a round shape that’s a little concave in the middle. You may go a bit bigger than the traced circles - I just look at them as a rough guide for shape and placement.
Bake the meringues for 50 minutes,
Once your timer goes off, turn the oven off - without opening the oven door - and let the meringues cool in the oven for several hours. The baking of the meringues can be done the day before, if needed!