1. Heat oven to 325°F Combine all spice mixture ingredients in small bowl. Heat Dutch Oven over medium-high heat until hot. Add 1 tablespoons of the oil; heat until hot. Cook pork, in batches, 4-6 minutes or until golden brown on all sides, adding more oil and/or adjusting heat, as needed. Place pork in a large bowl. Sprinkle with 1/4 cup of the spice mixture; toss to coat.
2. Add remaining 1 tbsp oil to Dutch Oven. Cook onions over medium heat for 3 minutes or until slightly soft, stirring occasionally. Add bell peppers; cook and stir for 2 minutes, until slightly soft. Add garlic; cook and stir for 1 minute. Stir in remaining spice mixture. Nestle pork in vegetables; pour tomatoes over mixture. Bring to boil; cover.
3. Bake 1 hour 15 minutes to 1 hour 30 minutes or until pork is fork tender.
4. Place masa harina in small cup; stir in water until smooth. Stir into pork mixture; bring to a boil over high heat. Boil 2-4 minutes or until slightly thickened, stirring frequently.