Wash the lemon, dab dry and cut off the ends. Quarter the lemon. Peel onions and garlic. Cut onions into slices, halve garlic. Wash the rosemary and dab dry.
Wash chicken thoroughly inside and out, dab dry and season with salt and pepper. Put lemon pieces, onions, garlic and rosemary into the chicken and close the opening. Tie the legs and wings together with kitchen string.
Heat the olive oil in a roasting pan, fry the chicken legs on both sides. Then place the chicken on the breast side and roast it in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 1 - 1 1/4 hours.
In the meantime, add poultry stock and in the last 10-15 minutes lemon juice. Turn the chicken halfway through the cooking time. In the meantime wash and drain the rice. Bring 500 ml salted water to the boil, add rice, stir and simmer covered over a low heat for 12-15 minutes.
Wash the coriander, dab dry and chop except for a little to garnish. Pour the finished rice onto a sieve, rinse briefly under hot water and drain. Mix the coriander with the rice.
Lift the chicken out of the stew. Bring the stock to the boil, stir the cornflour with a little cold water until smooth and stir into the stock. Let it boil again for about 1 minute. Season to taste with salt and pepper. Carve the chicken into small portion pieces and arrange on plates with the coriander rice.
Pour some sauce over the meat and serve garnished with fresh coriander.