Heat the olive oil in a large pot over medium heat. Add the onion and cook for about 5 minutes, until softened. Add the garlic and ginger and cook for another minute.
Add the garam masala, cumin, turmeric and chilli powder and cook for 1 minute.
Stir in the tomato purée and gluten-free soy sauce/tamari. Add the chopped tomatoes and coconut milk and bring to a gentle simmer.
Add the cauliflower florets and simmer for about 12–15 minutes, until almost tender.
Meanwhile, cut 500–600 g chicken breast into bite-sized pieces and briefly brown in a separate pan for about 3–4 minutes. It doesn’t need to be fully cooked yet.
Add the chicken to the curry for the last 5 minutes, until cooked through and the cauliflower is tender.