Part 1: Preparing the Batter

1. Preheat and Prepare Pan: Position a rack in the lower third of your oven and preheat to 325°F (165°C). Do NOT grease the tube pan. The batter needs to cling to the sides of the pan to climb and achieve its full height. Ensure your pan is completely clean and dry.
2. Combine Dry Ingredients: In a very large mixing bowl, whisk together the sifted cake flour, 1 cup (200g) of the granulated sugar, the baking powder, and the salt. Make a well in the center.
3. Mix the Wet Ingredients: In a separate medium bowl, whisk together the egg yolks, ¾ cup mango purée, vegetable oil, water, and vanilla extract until smooth and uniform in color.
4. Combine Wet and Dry: Pour the wet yolk mixture into the well of the dry ingredients. Whisk everything together until you have a smooth, thick, and homogenous batter. Set aside.

Part 2: Whipping the Egg Whites (The Meringue)

1. Start Whipping: In the clean, dry bowl of a stand mixer fitted with the whisk attachment (or in a large bowl with an electric hand mixer), place the 7 egg whites. Make sure there is absolutely no trace of yolk or grease in the bowl or on the whisk.
2. Add Stabilizer: Beat the egg whites on medium speed until they become foamy. Add the ½ teaspoon of cream of tartar.
3. Add Sugar Gradually: Increase the speed to medium-high. Gradually add the remaining ½ cup (100g) of granulated sugar, one tablespoon at a time, allowing it to incorporate before adding the next.
4. Whip to Stiff Peaks: Continue to beat until the meringue is thick, voluminous, and has formed stiff, glossy peaks. This means when you lift the whisk out of the meringue, the peak that forms holds its shape and doesn’t droop. Be careful not to over-whip, which can make the meringue look dry and clumpy.

Part 3: Folding and Baking

1. Lighten the Batter: Scoop about ⅓ of the stiff meringue into the mango batter bowl. Using a large rubber spatula, gently fold it in to lighten the batter. Don’t worry about being too gentle with this first addition.
2. Fold in Remaining Meringue: Add the remaining meringue to the batter. Now, be very gentle. Use a “folding” motion: cut the spatula down through the center of the mixture, scrape along the bottom of the bowl, and lift the batter up and over the top. Rotate the bowl a quarter turn and repeat. Continue this motion just until no white streaks of meringue remain. It is crucial not to stir or overmix, as this will deflate the air you worked so hard to incorporate.
3. Fill the Pan and Bake: Gently pour the batter into the ungreased 10-inch tube pan. Smooth the top lightly with your spatula. Bake for 60-70 minutes, or until the top is a deep golden brown and a long wooden skewer inserted into the center comes out clean. The cake will have risen significantly and may have a crack on top, which is normal.
4. Invert to Cool: This is a critical step! As soon as you remove the cake from the oven, immediately invert the pan and rest it on its “feet” or over the neck of a bottle (a wine or soda bottle works well). Let the cake hang upside down and cool completely for at least 2 hours. This prevents the cake’s delicate structure from collapsing on itself while it cools and sets.

Part 4: Frosting and Finishing

1. Release the Cake: Once completely cool, turn the pan right-side up. Run a thin, flexible knife or offset spatula around the outer edge and around the center tube to loosen the cake. Invert the cake onto a serving platter.
2. Make the Frosting: In a chilled bowl, whip the very cold heavy cream, sifted powdered sugar, and vanilla extract until soft peaks form. Add the chilled ¼ cup of mango purée and continue to whip until firm, spreadable peaks form. Be careful not to over-whip into butter.
3. Frost and Decorate: Frost the top and sides of the cooled cake with the mango whipped cream. Garnish with fresh mango slices, toasted coconut, or mint sprigs, if desired.