Heat ½ cup oil in a pot and fry 2 sliced onions until golden brown.
Add nigella seeds, mustard seeds, cumin seeds, along with green and red chillies.
Add 2 blended tomatoes and cook for 1 minute.
Add spices: red chilli powder, crushed chillies, salt, coriander powder, turmeric powder.
Cook for 2 minutes until oil separates.
Add cauliflower (gobi) and potatoes (aloo). Mix well.
Pour ½ cup water, cover, and cook on high flame for 3-4 minutes in pressure cooker.
Garnish with lemon juice, julienned ginger, fresh green chillies, coriander leaves, and a pinch of garam masala.
Serve hot with roti, paratha or naan.