How to Make It
Preheat oven to 200°F. Line two baking sheets with parchment paper.
In the bowl of an electric mixer fitted with the whisk attachment, beat egg whites on medium speed until frothy, 3 to 4 minutes. Add cream of tartar and beat an additional 2 minutes.
In a small bowl, mix sugar, cornstarch, and baking powder. With the machine running at medium-high speed, gradually add the sugar mixture 1 tablespoon at a time until meringue is shiny and stiff peaks form, 10 to 12 minutes. Beat in vanilla extract.
Using a 2-inch ice cream scoop [or soup spoon], scoop and drop meringue onto the prepared baking sheets, spacing at least 1 inch apart. Bake meringues until they are dry and peel easily from parchment (they should feel light and hollow), rotating halfway through, 70 to 80 minutes. Let cool completely in turned off oven for at least 6 hours or overnight without opening the door (meringues will crisp as they cool.)
Right before serving, place freeze-dried fruit in the bowl of a food processor and pulse to a fine powder. Sprinkle fruit dust over meringues.
Meringues without the fruit dust can be made up to 2 days ahead. Keep in an airtight container between sheets of parchment or wax paper.