Pat the chicken dry with paper towels.
Season both sides with salt and pepper.
Heat olive oil in a skillet over medium heat.
Add chicken and sear 4 minutes per side.
Remove chicken and set it aside.
In the same pan, add chopped onion.
Sauté until soft, around 3 to 4 minutes.
Add garlic, ginger, cumin, and coriander.
Stir until fragrant, about 1 minute.
Pour in coconut milk and mix well.
Add lime juice, zest, fish sauce, sugar.
Let sauce simmer for 3 to 4 minutes.
Return chicken to the pan carefully.
Simmer covered for 15 to 20 minutes.
Uncover and cook 5 more minutes.
Stir in cilantro before removing from heat.
Check for salt and pepper, adjust.
Serve hot with your favorite sides.