Mix all ingredients for the cauliflower batter in a bowl: all-purpose flour, cornstarch, red chili powder, kashmiri lal (optional), black pepper, and sea salt. Add water and stir to form a thick batter. Coat the cauliflower florets in the batter.
To fry the cauliflower, heat a pot over medium heat with enough oil for the florets to fry. Fry the cauliflower in batches. I fried 2 batches of cauliflower and air-fried 1 batch. Turn the florets so all sides get crisp and brown. Take the fried cauliflower out and place on a plate lined with a napkin or paper towel.If air frying, place the battered florets onto parchment paper and air fry for 10-12 minutes at 400 F. I haven't tried baking in the oven, but it should take about twice as long. Heat a pan or wok over medium heat. Add 1 tbsp avocado oil. When the oil is hot, add garlic, green chiiis, and ginger. Stir frequently for 2 minutes. Add red onions and scallion whites. Stir for about 4 minutes. (If you want to add a green bell pepper, you would add it now and proceed with the next step when the bell peppers are mostly cooked.)
Add tomato paste and let the tomato juices evaporate before adding ground coriander and black pepper. Stir the spices into the tomato mixture. Add chili garlic sauce and soy sauce.
Make the cornstarch slurry by mixing 1 tbsp cornstarch and ½ cup water in a small bowl. Add the cornstarch slurry and stir frequently until you have a thick sauce. Taste and add more soy sauce or salt if needed.
Toss the fried cauliflower in. Stir until the sauce adheres to the cauliflower. Garnish with scallions and serve immediately with rice or noodles.