Begin by heating the oil in a pan over medium heat. Add the chopped onions and sauté until they become soft and translucent. Introduce the minced ginger and crushed garlic to the pan, stirring for about 2 minutes until the mixture becomes fragrant.
Next, add the potato wedges and cauliflower florets to the pan. Lower the heat, cover the pan, and cook the vegetables, stirring occasionally to prevent burning. Once the vegetables are halfway cooked, mix in the tomato paste or chopped tomatoes. Continue cooking for another 3-4 minutes until the vegetables are tender but not mushy.
Incorporate the spice powders—coriander, turmeric, cumin, and red chili—into the vegetable mix. Stir well to ensure the spices are evenly distributed. Allow the spices to cook through for about 2 minutes until their raw aroma fades. At this point, the potatoes and cauliflower should be roasted and dry. Season with salt.
Finally, sprinkle a pinch of garam masala over the dish and garnish with a generous amount of chopped coriander leaves. Give it a final stir to combine all the flavors before serving.