Heat first 7 ingredients in a dry skillet over medium heat about 3 minutes or until fragrant, stirring often. Transfer spice mixture to blender or food processor; add onion, vinegar, ginger, sugar, and garlic; process 2 minutes or until well blended.
Combine pork and spice mixture in a glass bowl, tossing to coat. Cover and chill 30 minutes.
Heat a Dutch oven over medium heat. Coat pan with cooking spray. Add half of pork mixture; cook 5 minutes or until pork begins to brown, stirring often. Transfer to a bowl. Repeat process with cooking spray and remaining pork. Add broth to pan, scraping pan to loosen browned bits. Add pork mixture to pan. Stir in potato, salt, and tomatoes; bring to a boil. Cover, reduce heat, and simmer 1 hour or until potato is cooked and pork is tender, stirring occasionally. Garnish with cilantro, if desired.