Preheat the oven to 350°F.
The recipe is very simple. We need a baking dish; I am using an 8-inch x 6-inch Pyrex dish.
In a baking dish, combine the mangoes, crushed pineapple, sugar, lemon juice, and cornstarch. Mix well.
Sprinkle the cake mix evenly over the fruits.
Spread the sliced butter evenly over the cake mix.
Bake until the topping is lightly brown and looks crispy, and the filling is bubbly for about 35-40 minutes.
For the best taste, serve warm. If desired, serve with a scoop of ice cream, or whipping cream.
To Make Ahead: Mango pineapple cobbler is best served immediately, but it can be kept covered in the fridge for up to 5-6 days. Before serving, heat the cobbler in the microwave.