In a bowl, mash the mango well. I used a pastry blender but a fork could also work well here. Then stir in the sugars, egg, oil, juice, and zest.
In a smaller bowl, whisk together the flour, baking soda, and salt. Add the dry ingredients to the wet and stir until just combined. Then stir in the chopped cashews.
Add the mixture to a prepared baking pan. And bake at 325°F. If you are using small loaf pans like the ones pictured, bake for around 25-28 minutes. If you are using a standard size loaf pan, bake for around 50-55 minutes. Either way, insert a toothpick to check if the loaf is done before removing from the oven to allow to cool.