In a medium bowl, combine the chicken breast, Greek yogurt, lemon juice, 0.5 tsp of garam masala, and turmeric; toss to coat and marinate for at least 15 minutes.
Heat the olive oil in a large skillet over medium heat and sauté the diced onion until it becomes soft and translucent.
Stir in the minced garlic and ginger, cooking for about 1 minute until the mixture is fragrant.
Add the marinated chicken to the skillet and cook until the pieces are browned on all sides, about 5-7 minutes.
Pour in the tomato puree, the remaining 1 tsp of garam masala, cumin, sea salt, and black pepper, stirring well to combine.
Reduce the heat to low and simmer the sauce for 10 minutes to allow the flavors to meld and the chicken to cook through.
Stir in the coconut milk to create a creamy consistency and simmer for an additional 2 minutes.
Serve the chicken tikka masala over the warm cooked basmati rice and garnish with fresh cilantro before serving.