Heat the oil in a 10.5-inch skillet over medium-high heat. Add the onion and cook until it starts to turn translucent, about 2 minutes. Add the rice and cook, stirring frequently, until the rice changes to a milky white color and sounds and feels heavier, about 5 minutes. Add the garlic and cook for another minute. Stir in the water, tomato sauce and sea salt and place jalapeño in middle of pan. Reduce heat to low, cover with a lid and cook until water has been absorbed and rice is tender, about 20 minutes. Remove from heat and let sit, covered, for 5 minutes. Fluff with a fork, garnish with fresh cilantro and serve.