Chop the guavas into fine pieces or bite sized pieces depending on how you want it. Ensure that guavas are not too ripe or too raw, just right to cut into pieces. Transfer it into a bowl. Add the spices (chaat masala, red chilli powder, cumin powder and salt).
Add finely chopped coriander leaves.
Squeeze lemon juice over it and give it all a good toss till everything is mixed well.