In a medium heavy pot with a tight fitting lid, heat oil on medium heat and saute scallions, cilantro and garlic for about 2 minutes. Add tomatoes and saute another minute. Add rice and saute 2 minutes longer, stirring frequently. Add water, bullion cube and sazón. Taste the water for salt and add more to taste. Let water boil on a high flame stirring once. As the water boils down and just skims the top of the rice, turn the flame to very low and cover 15 minutes. The steam will cook the rice so do not open. After 15 minutes, shut the flame and let the pot sit for at least 5 more minutes. This will finish cooking the rice without burning the bottom.