Preheat the oven to 425 degrees F. Line a baking sheet with parchment paper.
Sift together the flour, cornstarch, cream of tartar, and baking soda into a bowl. Separate the eggs into two bowls. Beat the whites to soft peaks. Add the sugar to the egg whites in 3 stages, beating after each addition to make a stiff, glossy meringue. Whisk in the egg yolks, 1 at a time. Sift the dry ingredients together, then sift them over the egg mixture, and fold them in with the whisk, without beating or you'll lose volume.
Pipe or drop by tablespoonfuls onto the baking sheets, leaving room between them so they can spread. Bake until lightly golden, about 5 to 7 minutes. Remove the cakes to a rack to cool. They will harden slightly as they cool.
Sandwich the rounds together with raspberry jam and sweetened and vanilla-flavored whipped cream. Let the sweets sit an hour or so to soften before serving.
This is important. They will not be sponge-like right away, and you want them to be. They need no dressing up, in my opinion, but you can dust with icing sugar (confectioners') before serving if you like.