Heat oil in a pan and add cumin seeds. Allow cumin seeds to sizzle, and then add chili and ginger. Saute for a few seconds.
Add chopped tomatoes and mix well. Cook for a minute and then add turmeric powder, chili powder, and coriander powder.
Mix everything well, and continue cooking until tomatoes are soft and oil separates from the sides, about 3-4 minutes.
Add cauliflower, potatoes, and salt to taste. Mix well and stir-fry for 3-4 minutes.
Turn the heat on low-medium, cover the lid, and continue cooking the vegetables for 10-15 minutes. Stir the vegetables 2-3 times in between. The cooking time may vary, so keep an eye on vegetables.
Cook the vegetables until they are cooked, and the moisture is absorbed.
Note: Sometimes, cauliflower releases lots of water. So if the vegetables are cooked but still see the moisture, turn the heat on medium-high and remove the lid. Cook until all the moisture is evaporated. The vegetables should be well cooked but not soggy.
Once the vegetables are cooked, and all the moisture is absorbed, add garam masala, coriander leaves, and lemon juice.
Mix well, turn off the heat and transfer Aloo Gobi to a serving bowl.