Preheat a convection oven to 400°F (200°C) and line a heavy-duty rimmed baking sheet with parchment paper.
In a large stainless steel mixing bowl, combine cauliflower florets with olive oil, cumin, paprika, turmeric, coriander, cinnamon, garlic powder, and salt.
Toss the cauliflower vigorously until the spice slurry achieves total surface coverage on each floret.
Distribute the florets across the baking sheet in a single layer to ensure proper heat circulation and Maillard reaction.
Roast for 25 to 30 minutes, agitating the pan halfway through the duration, until the cauliflower exhibits charred edges and a tender internal texture.
Prepare the dressing by whisking tahini, lemon juice, minced garlic, and warm water in a small bowl until a smooth, pourable emulsion is formed.
Assemble the bowls by layering 0.5 cups of cooked quinoa as the base in four separate vessels.
Equitably distribute the roasted cauliflower, tomatoes, cucumbers, and red onion atop the grain base.
Add a 2-tablespoon quenelle of hummus to each bowl.
Finish by drizzling the tahini emulsion over the components and garnishing with chopped parsley.