In a large pan over medium heat, add the oil and the chorizo. Sautué for 5 minutes or until the chorizo is brown. Remove and set aside.
Add the onions, tomatoes, scallion and garlic to the pan and sautué for about 7 minutes or until translucent. Add the rice and stir to coat.
Add the chicken stock, stir and bring to a boil. Add the chorizo and color. Reduce the heat, cover and cook for about 15 minutes.
Add the shrimp and cook for about 15 minutes more. Turn the heat off and fluff the rice with fork. Add the fresh cilantro and stir. Cover and let sit for 5 minutes.