Preheat oven to 350°F (180°C). Liberally grease two 8″ or 10″ round cake pans or a bundt pan with vegetable shortening, and/or spray with baking spray.
Combine flour, sugar, baking powder, salt, and pudding mix in a large mixing bowl. Add in eggs and water, beating just until smooth. Carefully add melted butter and vanilla to the batter, mixing on medium speed until smooth.
Divide batter evenly into two bowls. Add mango pulp to one bowl, and pureed strawberries to the other. Stir both until everything is fully incorporated and smooth. Use food coloring to tint mango batter more orange / yellow, and strawberry batter more red, if desired.
Divide batter among prepared cake pans, and marble** batters together. Bake until golden and knife inserted into center of batter comes out clean and cake springs back – about 45-60 minutes.
Allow to cool 10-15 minutes before turning cakes out onto baking rack to cool fully. Ideally, allow to cool to room temperature, wrap tightly with plastic wrap. Allow cake to sit overnight, make frosting & ice cake the following day.
Prepare either American or Swiss meringue buttercream, flavoring with either mango pulp or strawberry puree.