Cut the chicken breast into bite-sized 1-inch pieces and set aside.
Heat the ghee in a large skillet over medium heat until melted and shimmering.
Add the diced yellow onion to the skillet and sauté for 4-5 minutes until translucent and soft.
Stir in the minced garlic and grated fresh ginger, cooking for 1 minute until fragrant.
Add the chicken pieces to the pan and cook for 5-6 minutes, turning occasionally until browned on all sides.
Sprinkle the garam masala, turmeric, sea salt, and black pepper over the chicken and stir to coat evenly.
Pour in the tomato puree and full-fat coconut milk, stirring to combine into a smooth sauce.
Reduce the heat to low and simmer for 8-10 minutes until the sauce has thickened and the chicken is cooked through.
Fold in the baby spinach and cook for 1-2 minutes until just wilted.
Remove from heat and garnish with chopped fresh cilantro before serving.