1Remove fat from pork. Cut pork into 2-inch cubes. In blender, place onion, garlic, gingerroot, turmeric and red pepper. Cover; blend on medium-high speed about 1 minute, stopping blender frequently to scrape sides, until smooth.
2In 4-quart Dutch oven, heat oils over medium heat. Gradually and carefully pour blended mixture into oil (oil will spatter). Heat to boiling. Reduce heat; cover and simmer 15 minutes, stirring occasionally.
3Stir in pork, tomatoes, lemon grass and fish sauce. Heat to boiling. Reduce heat; cover and simmer about 1 hour 30 minutes, stirring occasionally, until pork is tender. Serve over rice; garnish with cilantro.