Finely chop 1 onion and cut 2 onions into distinct thick square petals.
Heat 1 tbsp vegetable oil in a skillet, sauté onion petals for 2 minutes until tender-crisp; remove and set aside.
Add remaining oil, crackle cumin seeds, and sauté chopped onions, ginger paste, and garlic paste until golden.
Add chopped tomatoes, turmeric powder, red chili powder, and salt; cook until soft.
Add chopped target vegetables and sauté uncovered for 10 minutes, then fold in onion petals and amchur powder before serving.