Adjust oven racks to the two lowest positions. Preheat the oven to 375° F. Line two cupcake pans with paper liners. In a small mixing bowl, sift together the flour, ¾ cup of the sugar and the salt; set aside. In the bowl of an electric mixer fitted with the whisk attachment, beat the egg whites with the vanilla and cream of tartar on medium-high speed until soft-medium peaks form. Gradually add the remaining ¾ cup sugar, continuing to beat until stiff peaks form. Gently fold in the dry ingredients using a rubber spatula, being careful not to deflate the batter.