Whisk together garlic powder, onion powder, turmeric, garam masala, red curry powder, ground coriander, ground cumin, paprika, and 1 tablespoon kosher salt in a medium bowl.
Place the cubed chicken in a large bowl and mix with the spice blend and Greek yogurt until evenly coated. Cover and refrigerate to marinate for at least 30 minutes or up to 24 hours.
Rinse the basmati rice under cold water until the water runs clear and set aside.
Set the Instant Pot to Sauté and heat the canola oil. Add the marinated chicken and let it sear undisturbed for 1 minute, then stir and cook until lightly browned (work in batches if needed). Scrape any browned bits from the pot to avoid burning.
Add the diced onion to the pot and cook for about 1 minute, stirring occasionally, then add the minced garlic and grated ginger and stir to combine.
Stir in the tomato paste, then add the diced tomatoes and 3/4 cup chicken broth; stir gently to combine.
For pot-in-pot rice: add the unsalted butter to a heatproof bowl, then add the rinsed rice, 2 cups water, and 1/4 teaspoon kosher salt; stir to combine and cover the bowl.
Place a long-leg trivet on top of the chicken in the Instant Pot, set the covered rice bowl on the trivet, close the lid, and ensure the valve is set to Sealing.
Cook on High Pressure for 4 minutes. When the cook time ends, allow a natural pressure release for 10 minutes, then carefully do a quick release for any remaining pressure.
Open the lid and remove the rice bowl; keep it covered with foil and set aside. Fluff the rice with a fork just before serving.
Select Sauté again, gently stir the chicken tikka masala, and simmer for 15–20 minutes until the sauce reduces and thickens, stirring occasionally to prevent sticking.
Stir in 1/2 cup heavy cream and taste for seasoning; add up to the remaining 1/2 cup cream if desired for a richer sauce.
Serve the chicken tikka masala over the basmati rice and garnish with chopped fresh cilantro.