In a small mixing bowl, combine the diced chicken breast with Greek yogurt, lemon juice, garam masala, and turmeric; let it marinate for at least 15 minutes.
Heat the olive oil in a large skillet over medium heat and sauté the diced yellow onion until it becomes translucent and soft.
Stir in the minced ginger and garlic, cooking for about 1 minute until the mixture is fragrant.
Add the marinated chicken to the skillet, increasing the heat slightly to brown the chicken on all sides.
Pour in the tomato puree, ground cumin, and sea salt, stirring well to combine all ingredients.
Reduce the heat to low and simmer the sauce for 10 to 12 minutes until the chicken is fully cooked through and the sauce has thickened.
Stir in the full-fat coconut milk to create a rich, velvety texture and heat through for another minute.
Serve the chicken tikka masala over a bed of warm, fluffy basmati rice and garnish with freshly chopped cilantro.