Preheat the oven to 200°C.
In an oven-safe pan, drizzle olive oil and place the cauliflower and onions.
Pour the rice evenly in between the cauliflower pieces.
Mix all the ingredients for the red sauce in a bowl.
Pour the sauce gently over the rice and cauliflower.
Cover the pan with wet parchment paper and cover with aluminum foil on top of it.
Bake it in a preheated oven at 200°C for 1 hour.
Remove the parchment paper and aluminum foil.
Transfer to the broil for 5-7 minutes to get a golden brown color.