In large saucepan over medium heat, cook and stir onion and garlic in oil until onion is translucent, about 5 to 7 minutes. Add pork, cook and stir 2 to 3 minutes or until the pork begins to turn white.
Stir in tomatoes, cilantro, jalapeno, salt and pepper; bring to a boil. Reduce heat; cover and simmer for 10 minutes or until pork is tender.
Meanwhile, in small bowl, blend together water and cornstarch until smooth, stir into pork mixture until the sauce thickens slightly. Spoon stew into individual soup bowls.