Coarsely grind the cumin seeds, coriander seeds, nigella seeds, fennel seeds, and mustard seeds to make the achari masala.

Make deep cuts across the whole chicken so the marinade can penetrate the meat.

Combine lemon juice, red chili powder, 1 teaspoon ground coriander, ground cumin, 1/2 teaspoon garam masala, chili flakes, 1 teaspoon salt, black pepper, yellow food coloring, chicken tikka masala, and the achari masala in a bowl.

Rub the spice marinade thoroughly over the chicken, working it into all the cuts.

Cover and marinate the chicken for 120 minutes in the refrigerator.

Pour 4 cups of water into a large pot and bring it to a simmer over medium-high heat.

Set the steamer basket over the pot and place the marinated chicken inside it.

Cover and steam the chicken for 20 minutes over medium-high heat, collecting the chicken drippings in the water below.

Remove the steamed chicken and reserve the flavorful chicken-dripping stock for the rice.

Brush the steamed chicken with 1 tablespoon of cooking oil and place it on a baking tray.

Grill the chicken in a preheated oven for 10 to 15 minutes until the exterior is crisp and browned.

Heat the remaining cooking oil in the rice pot over medium heat and add 1 teaspoon cumin seeds.

Add the sliced onion and sauté until softened and lightly golden.

Add the chopped tomato and remaining 1 teaspoon ground coriander, then cook until the tomato softens.

Stir in the green chili, 2 1/2 teaspoons salt, and 1/2 teaspoon garam masala.

Mix the saffron with 1/4 cup water, then pour it into the pot with the reserved chicken-dripping stock.

Bring the rice cooking liquid to a boil and add the basmati rice.

Cook the rice uncovered until the liquid has nearly evaporated and small steam holes appear on the surface.

Sprinkle the remaining 1/2 teaspoon garam masala over the rice and cover the pot tightly.

Steam the covered rice on low heat for 10 minutes, then fluff it gently.

Spread the achari rice on a serving platter and arrange the crisp steam-roasted chicken on top.