Dice 1 large ripe avocado, 1 medium-sized cucumber, 1 medium-sized onion, and 1 medium-sized tomato into small pieces.
In a large mixing bowl, combine the diced avocado, cucumber, onion, and tomato.
Finely chop 1 green chili and a handful of fresh coriander leaves. Add them to the mixing bowl.
In a separate small bowl, prepare the dressing by mixing the juice of 1 lemon, 1 teaspoon chaat masala, 1/2 teaspoon black salt, and 1/2 teaspoon red chili powder. Adjust the seasoning according to your taste.
Pour the dressing over the chopped vegetables and avocado in the mixing bowl. Gently toss the salad to mix well and coat the ingredients evenly with the dressing.
Refrigerate the salad for 15-20 minutes to allow the flavors to meld.
Serve the chilled Avocado Kachumber Salad in a serving bowl or plate.