Peel the mangoes, dice, also dice the onion.
Heat the oil in a large pan medium-low heat, add the red flake pepper, and toast for a few seconds don’t burn it.
Add ground cinnamon.
Add the diced pineapple
Also, add the diced mangoes
After you've brought the mixture to a boil, season with salt then reduce the heat and continue the cooking until the fruits are very soft.