Heat oil in a deep skillet over medium heat, then add cumin seeds and let them crackle for about 30 seconds, releasing their aroma.
Add the finely chopped onion to the pan, stirring frequently until it turns golden and translucent, about 5 minutes, filling the kitchen with a sweet, caramelized smell.
Stir in the minced garlic and grated ginger, cooking for another minute until fragrant; it will smell spicy and warm.
Add the chopped tomatoes and soaked dried red chilies to the pan, cooking and stirring until the tomatoes break down and the mixture thickens, about 8–10 minutes. The sauce will turn a deep red and cling to the vegetables.
Mix in the ground coriander, turmeric, and garam masala, cooking for another minute to toast the spices and release their flavors.
Add the mixed vegetables to the spice mixture, stirring well so they are coated with the sauce. Sauté for about 5 minutes until slightly tender.
Pour in water or vegetable broth, then season with salt to taste. Bring everything to a gentle boil, then lower the heat to simmer uncovered.
Let the curry simmer for about 15–20 minutes, stirring occasionally. The vegetables will become tender, and the sauce will thicken into a rich, velvety consistency.
Taste and adjust the seasoning with more salt if needed, then turn off the heat. The dish will have a vibrant color and a fiery, aromatic flavor.