Making the tomato sauce: Heat a tablespoon of olive oil in a skillet over low heat. Add the tomatoes and garlic.Cover and simmer until the tomatoes are cooked through, mash them with a potato masher. Add oregano, and salt and pepper to taste. Set aside.
Making the filling: While you are making the sauce, soak the rice in enough water to cover it, plus an inch. Let it rest for an hour.Heat the oil over very low heat, add the onion and garlic, cook and stir until they start to release their aroma. Stir in the chicken, salt, pepper, and hot sauce, increase heat to medium and simmer covered for five minutes.
Cooking rice: Remove all rice from the water. Add the rice to the pan and stir. Add 1 cup of the water in which the rice was soaked and a cup of the tomato sauce you prepared previously (set the rest aside). Simmer until almost all the liquid evaporates. Cover tightly, lower heat to the minimum, and simmer for five minutes. Remove the pan from the heat. Mix in the chopped basil.
Cleaning peppers: Cut a slit in the cubanelle peppers and scoop out the seeds and white parts with a small spoon.
Stuffing peppers: Preheat oven to 400 ºF [200 ºC].Stuff the cubanelle peppers with the chicken mixture.
Roasting peppers: Pour the remaining tomato sauce on a baking pan big enough to accommodate the peppers, or divide between two smaller pans (which is what I did). Place the peppers on the tomato sauce. Cover tightly with aluminum foil. Bake for 25 minutes. Remove from the oven, garnish with the basil leaves and serve.