Start the chicken: combine the tomato paste, half of the olive oil, paprika, chilli powder and lemon juice in a large bowl. Mix well, then add the chicken and toss to coat completely.
Place the remaining oil in a large heavy-based frying pan and add the chicken, skin side down. Cook over medium heat for 6–8 minutes, until the skin renders and starts to brown. Transfer to a tray (it won't be fully cooked yet, that's okay).
Cook the sauce: add the rice to a bowl of water, enough to cover completely.
Dice the red onion and finely dice the carrot. Add to the pan and cook for 3 minutes, stirring, until softened.
Deglaze the pan with a little stock, scraping off the fond. Add the cinnamon and cumin, season with salt, and cook for 2 minutes until aromatic.
Drain the rice, add it to the pan and stir through the vegetables to combine.
Add the remaining stock and return the chicken to the pan. Bring to a simmer, then reduce to very low, cover, and cook for 15 minutes.
Finish: remove the chicken and set aside. Discard the cinnamon stick.
Stir the rice, then add the spinach. Cover, turn off the heat, and let sit for 2 minutes.
Uncover and stir the spinach through the rice. Serve with the chicken on top.
