Preheat oven to 375 F degrees.
Melt the butter. Then pour it into a 13"x 9"x 2" baking (or lasagna) pan.
In a bowl, using a fork combine well the flour, half the granulated sugar, baking powder and salt. Stir in the milk, mixing until just combined. Pour this batter over the butter. Do not stir them together.
Combine the frozen mango chunks, lemon juice, and remaining half of granulated sugar and several dashes of ground cinnamon and bring to a boil over high heat, 3 to 5 minutes, stirring constantly. Pour the mango mix over the batter. Do not stir them together.
Depending on your oven, bake from 38 - 45 minutes, until the bread top is golden brown. Serve warm or cold, on its own, with a dollop of whipped cream or with vanilla ice cream.