Preheat oven to 200 degrees celcius.
Spray peppers, chillies, garlic and tomatoes with olive oil spray and roast for 20-30 minutes till peppers are blackened and tomatoes are starting to burst.
Quickly pop vegetables into a plastic bag and seal to help steam off skin.
After 10 minutes, remove skin and pop ingredients into a blender, adding olive oil as you go, to make a smooth sauce.
Lastly, stir in yoghurt and optional mayonnaise, and serve.