How to Make It
Place a rack in middle of oven; preheat to 450ºF. In a large bowl, whisk together oil, 1 Tbsp. curry powder, 1/4 tsp. cumin, half of garlic and 1/4 tsp. each salt and pepper. Add cauliflower and toss to coat. Arrange in a flat layer on a large baking sheet and roast, stirring occasionally, until golden brown and tender, about 20 minutes. Transfer to a rack to cool slightly.
Bring 2 cups water to a boil. Add quinoa; return to a boil. Cover, reduce heat to medium-low and simmer until liquid has absorbed, 15 to 20 minutes. (Tilt pan to check; don't stir quinoa.) Remove from heat and let stand, covered, for 15 minutes. Fluff quinoa with a fork, transfer to a bowl and let cool.
In a small bowl, whisk together yogurt and remaining 2 tsp. curry powder, 1/2 tsp. cumin and garlic. Season with salt and pepper. In a large bowl, mix quinoa, spinach and half of dressing. Top with cauliflower and grapes and drizzle with remaining dressing; toss again. Sprinkle with cashews and serve.