Combine 35 oz (1 kg) of chopped mango cubes, 8 oz (200 g) sugar, and 2 tablespoon lemon juice in a pan and bring the mixture to a boil on medium heat, stirring occasionally.
Turn down to low heat and allow to simmer for 10 minutes. Stir at regular intervals using a wooden spoon or a silicone spatula while cooking.
Remove the pan from heat and let the mixture cool down to room temperature. Add the cooled mixture to a blender or a food processor and blend until smooth.
Store the coulis in an air-tight container in the refrigerator for up to 7 days or freeze for up to 6 months