Preheat oven to 400F. Chop 1 large head of cauliflower into bite-sized pieces. Toss with 3 tbsp olive oil and 1/4 tsp salt. Spread out on a baking sheet and bake 30 min, stirring halfway through. Stir 1/4 cup tahini with 3 tbsp water, 2 tbsp lemon juice and 1 minced garlic clove in a small bowl. Pour over roasted cauliflower. Sprinkle with 2 tbsp chopped parsley.