1Preheat oven to 350 degrees. Spray bundt pan liberally until coated. Flour pan if it is not a nonstick pan.
Take the cake mix out of the Duncan Hines Signature Tres Leches box and empty in a large bowl. Combine flour, baking powder, and salt.
2Beat egg yolks with 3/4 cup sugar on high speed until yolks are pale yellow. Stir in milk and vanilla. Pour egg yolk mixture over the flour mixture and combine. Add water, mix well.
Beat egg whites on high speed until soft peaks form. With the mixer on, pour in remaining 1/4 cup sugar and beat until egg whites are stiff but not dry.
3Fold egg white mixture into the batter very gently until just combined. Pour into prepared pan and spread to even out the surface.
Bake for 45 minutes or until a toothpick comes out clean. Turn cake out onto a rimmed platter and allow to cool.
Combine together condensed milk, evaporated milk, and heavy cream in a small pitcher. Then add the smaller content package [from cake mix box] to milk mixture, whisk until smooth, well blended. When cake is cool, pierce the surface with a fork several times. Slowly drizzle all but about 1 cup of the milk mixture—try to get as much around the edges of the cake as you can.
4Allow the cake to absorb the milk mixture for 30 minutes. To ice the cake, squeeze whipped topping in a circular motion around the cake. Fill in the hole/middle of bundt cake with whipped cream to desired level, creating a spiral mound of cream extending out the top. Keep refrigerated until ready to serve.