Mix sliced mangoes and apples with 1 teaspoon of the cinnamon, the nutmeg, and lemon juice. Place in a buttered Pyrex dish. Set aside.
Combine butter and brown sugar until well blended. Cut in flour and the remaining 1/2 teaspoon of cinnamon. Mix until crumbly. Sprinkle the topping evenly over fruit slices. Bake at 180 degrees C till golden.
Serve warm or cold, with cream or ice cream.