Wash the rice. Put the cleaned and grated onions and carrot in 3-4 tbsp oil with a little water, saute for a few min. Once they're left in just oil, sprinkle on some black pepper and salt to taste and pour in the rice that you've washed in several waters. Stir several times and pour in 2 1/2 cups water. Boil until the rice and veggies soften and the water evaporates. Take it off the stove.
Put rice filling in the seasoned chicken and sew it closed or fasten with toothpicks so it doesn't spill out during baking (use the leftover filling as a garnish - add it around the chicken with a little water a few min. before the chicken is ready and cook the rice and veggies during the final min.)
Insert pieces of butter in several spots under the chicken's skin, as well as on top of it.
Pour about 1 1/2 cups water in the container. Put the lid on and place in a cold oven. Turn it on to 392°F (200 °C) and bake until the chicken is cooked. During baking, pour in a little warm water (so the container doesn't crack) if needed.
Before removing from the oven, if needed, remove the lid so the chicken gets a golden crisp on top.
Serve the baked chicken with the rice filling and poured with the sauce from the baking.