Preheat the oven to 170℃.
Using your mixer, make a meringue by whisking your egg whites on high speed until soft peaks form and gradually add all the sugar. Keep mixing on high speed until smooth and glossy stiff peaks form.
Quickly fold in the lemon juice, vanilla extract, and cornstarch until well mixed. Try not to overmix as you will lose the trapped air which will make your cloud flat.
Dab a little bit of the meringue on the bottom corners of your parchment paper to secure it to your baking sheet. Skip this step if you’re using a silicone mat.
With your spoon, scoop a dollop of meringue on your baking sheet keeping in mind to leave a 2-inch gap between each one.
Using the back of your spoon, create a well in the middle of your meringues. This is where you will be placing your ice cream later on.
As soon as you place your meringues in the oven, lower the heat to 93℃ and let it bake for 1 hour and 45 minutes. Do not open the oven door once you place the meringues inside!
After baking, turn the oven off and let the pavlovas cool inside. When it has cooled down completely, you can serve them right away or place them in an airtight container and store at room temperature for up to 2 days.