Place all the ingredients for the sauce in the blender and process until smooth.
Bring sauce to a simmer in a sauce pot set to medium heat. Simmer for 5-7 minutes, season with salt and pepper. Set aside.
Sift the flour and cornstarch into a large bowl. Add the salt and soda water. Whisk until combined. The batter should have the consistency of a thick pancake batter. Add more water as necessary.
Heat oil in a large pot or Dutch oven to 350°F.
Once the oil is hot, use your hands to drop the cauliflower in the batter and then into the oil. Fry for 2-3 min. on each side or until the batter is crispy and slightly golden.
Remove from oil and place on a plate or tray lined with paper towels. Serve with spicy tomato sauce.
Notes
For a healthier version, season the cauliflower with salt, pepper and 1 tbsp. of oil. Roast the cauliflower in the oven at 450F for 20 min.