Heat the olive oil in a large nonstick ovenproof skillet over medium-high heat. Add the onion and cook until slightly softened, about 2 minutes. Add the garlic and taco seasoning and cook, stirring occasionally, until the garlic softens, about 1 minute. Stir in the tomatoes, rice and 3 cups water. Bring to a boil, then cover and reduce the heat to medium low. Cook until the rice is tender, about 20 minutes.
Preheat the broiler. Remove the skillet from the heat and stir in the chicken, 1 cup cheese, the cilantro and 1/2 teaspoon salt. Arrange the tortillas on top to cover and sprinkle with the remaining 1 cup cheese. Broil until the cheese melts, 2 to 3 minutes. Top with sour cream, pickled jalapenos and more cilantro.