Place the oven rack in the lowest position and preheat to 350F.
Sift together 1/2 cup of the sugar and the flour twice. Set aside.
Mix together the egg whites, cream of tartar, vanilla extract and salt. Beat on medium speed until soft peaks form. Gradually add the remaining 1 cup sugar, 2 tablespoons at a time, until stiff, glossy peaks form and the sugar has been dissolved. Fold in the flour mixture, half a cup at a time, until combined.
Gently pour the batter into an un-greased 10-inch tube pan. Use a butter knife to cut through the batter to make sure there aren't any air pockets. Bake until the top is browned and appears dry, 35-40 minutes. Remove from the oven and immediately invert until completely cooled.
Once cooled, run a knife around the outside of the cake to release from the pan, if needed. Split the cake into 2 layers horizontally. Place the bottom layer of the cake on an ovenproof serving plate*. Spread the lemon curd on top of the cake, then place the top layer over the curd.
To make the meringue, preheat the oven to 350F. Place the egg whites in a bowl with the cream of tartar and beat on medium until soft peaks form. Gradually add the sugar and continue to beat until stiff peaks form. Spread the meringue over the top and sides of the cake. Bake for 15-18 minutes, or until browned.
Notes
*If you don't have an ovenproof serving plate, you can also use a kitchen torch to brown the meringue.slightly adapted from TASTE OF HOMENutrition information provided as an estimate only. Various brands and products can change the counts. Any nutritional information should be used as a general guide.