In the same pan, add 1 tbsp oil.
Add mustard seeds and cumin seeds. Let them crackle.
Add sliced onions and sauté until golden brown.
Add green chilies and grated ginger. Cook for 1 minute.
Add tomatoes, turmeric, red chili powder, coriander powder, and salt.
Cook until tomatoes soften and the masala thickens (5–6 minutes).