1.Preheat the oven to 375 degree F. Line a 10 by 15-inch baking pan with parchment paper. Make sure the parchment paper is large enough to have at least 2-inch excess on all sides for easy removal when the cake is done.
2.Next, beat the egg whites with cream of tartar and salt until frothy. Then slowly add in around half of the sugar and beat until stiff peak forms.
3.In a separate bowl, beat the egg yolks with the remaining sugar until light and pale yellow. Then add 1 teaspoon vanilla, melted butter and mango puree until incorporated. Sift the cake flour into the egg yolk mixture. Fold egg whites into the egg yolk mixture in three batches. Be careful not to deflate the egg whites too much.
4.Gently spread the cake batter evenly onto the prepared cake pan. Bake for 12 minutes, or until a tooth pick inserted into the cake and comes out clean. Place on a wire rack and roll it up on the short end, wait until completely cooled. Meanwhile, work on the filling.
5.Beat the heavy cream with powdered sugar and 1/2 teaspoon vanilla until stiff peak forms.
6.Spread the whipped cream evenly onto the cooled cake. Sprinkle diced mango onto the cream evenly. Roll the cake up, from the shorter end. Wrap in plastic wrap and refrigerate for at least 1 hour.
7.Trim off 1/2-inch of the cake on both ends for a prettier presentation. Decorate with mango slices then cut into slices and serve.