Combine ginger, garlic, yogurt, lemon juice, paprika, garam masala, chili powder, turmeric, cumin, in a large bowl. Season well with salt and pepper. (It should be on the salty side, as this is a marinade.) If you'd like, you can blend the marinade together in the blender or food processor beforehand, but it's not necessary.
Add the chicken and toss to coat evenly. Let sit at least 30 minutes at room temperature, and up to overnight in the refrigerator.
Place oven rack in top third of the oven and preheat to 425ºF.
Meanwhile, prepare the cauliflower. Add the cauliflower to a large rimmed baking pan. Drizzle evenly with the olive oil. Sprinkle over the cumin seeds and ground turmeric. Toss together until evenly coated.
Remove chicken parts from the marinade and shake to leave excess marinade behind. Make spaces in the cauliflower for the chicken parts throughout the center of the pan. Roast in oven for 20 minutes, then toss the cauliflower to ensure it's cooking evenly, and return the pan to the oven for 25 to 30 minutes more (40 to 45 minutes total roasting time), until chicken and cauliflower are cooked through and the skin of the chicken is evenly browned. At the end of cooking, you can place the sheet pan under the broiler for 3-5 minutes to get the classic char / tandoor marks on the chicken, if you'd like.
While everything roasts, mix together the yogurt with garlic, lime juice and season with salt and pepper, set aside.
When everything is cooked, top with garnishes of your choice — we used dollops of seasoned yogurt, fresh herbs and scatter the red onion all over. Serve right from the pan.
Notes
alternatively, you can use 3 to 3 1/2 pounds of bone-in, skin-on chicken parts, such as breasts, thighs and legs). You can also use boneless, skinless chicken, adjust the cooking time, as it will take less time. It will take approximately 40 - 45 minutes for bone-in parts or 30 - 40 for boneless. (time may have to be adjusted more or less, given the size of the chicken parts) To the cauliflower, you can also include a can of chickpeas and/or 1 lb of Yukon Gold potatoes, zucchini, eggplant, etc