Preheat oven to 220 C/ 428 F.
Toss the red bell peppers in 1/4 teaspoon salt, pepper and some olive oil and spread them out on half the baking sheet. Toss the cauliflower florets in curry powder, olive oil, salt, paprika, cumin powder, lemon juice and the lemon zest and spread them out on the other half of the baking sheet.
Bake for 30-35 minutes in the preheated oven flipping the florets once in between. When ready, the cauliflower should be tender but with crisp and golden edges.
In the meanwhile, wash the quinoa really well in a colander. Add quinoa, water and salt to a saucepan and bring it to a quick boil. Then reduce the heat, cover and cook for 15-20 minutes till all the water is absorbed and the quinoa is cooked through.
To make the dressing, add all the ingredients except water to a jar and shake well. Check the consistency and if the dressing doesn't come together or is too thick, add water to the jar and shake again.
To serve, add 1/2-3/4 cup quinoa to a bowl and top with cauliflower and red bell peppers. Drizzle with tahini dressing and serve.