Heat oil in a large pot over medium heat. Brown chicken thighs on both sides, then set aside.
In the same pot, add chopped onion and garlic. Sauté until fragrant and translucent, then add the tamatoes.
Return the chicken to the pot. Season with salt, black pepper, and red pepper flakes.
Pour in chicken stock and bring to a simmer.
Stir in palm nut butter until fully dissolved into the broth.
Cover and simmer on low for 45 minutes to 1 hour, until the chicken is tender and the sauce is thick.
Serve hot with steamed white rice.