Make paste of garlic, red onion, fennel, cumin, ginger, 1/4 portion of the medium size onion, coriander, and chilies; to make it easier and smoother, add in 1 tbsp olive oil while grinding.
Heat 1-2 tbsp olive oil, saute sliced onion until translucent; add in paste and followed with chicken, a sum of water, and lemon grass. Turn chicken to coat.
Add in coconut milk, 1/4-1/2 cup tomato sauce, and 1-2 tbsp fresh lemon/lime juice. Add in seasonings, stir well.
Let simmer until chicken is well cooked and gravy thickened.
Add more chilies when you want it more hotter. Add more tomato sauce for redder color. Add more lemon/lime juice to make it more sour