Cauliflower steaks with zahter

Name: Cauliflower steaks with zahter
Prep time: 15 min
Cook time: 45 min
Total time: 1 h
Ingredients: 2 large cauliflowers, trimmed and leaves discarded (1.3kg); 70g unsalted butter; 2 sprigs of sage (6g); 8 strips of finely shaved lemon skin; 1½ tbsp tahini paste; 1 tbsp lemon juice; 3 tbsp olive oil (or 60ml, if using oregano instead of the zahter); 1 onion, finely chopped (170g); 1 tbsp cider vinegar; 1 tsp honey; 3 tbsp zahter, drained from its oil (or 3 tablespoons of picked oregano leaves); 20g baby capers, pat dried; 5g coriander, roughly chopped; Salt