Dice half of the mango pulp or roughly chop it into tiny pieces. Transfer to a bowl. Add granulated white sugar. Mix nicely. Set aside for 10 - 15 minutes. After 10 minutes, sugar will be completely dissolved with the mango pulp and a yellow color juice will be released. Do not rush this process.
Transfer the mango pulp along with all the yellow liquid to a saucepan. Turn on the stovetop heat to low. Start cooking the jam.
Blend the remaining half of the mango pulp without any water. Add to the simmering pulp along with the lemon juice. Stir to combine.
Stage 1, the jam will be watery, with big chunks of mango. Keep cooking on low heat, while stirring at regular intervals.
Slowly, the texture of the jam would thicken a bit. Use a potato masher or a ladle to gently mash the mango pieces. Keep stirring at regular intervals.
After 15 – 20 minutes on low heat, the mango pieces mashed nicely, and the jam will start sticking to the spoon. Turn off the heat.
To check the consistency of the mango jam, spread a big tablespoon of jam on a plate. The mango jam should be thick, doesn't drop off easily, and will stick to the plate. Else continue to cook further.
Allow the mango jam to cool down completely at room temperature. Store the cooled mango jam in a clean, sterlisied glass jar with a tight fitting lid.
Serve mango jam on a bread slice or store in the refrigerator.