Heat the oil in a dutch oven over medium-high heat. When the oil is hot add the pork pieces and cook, stirring occasionally, until pork is browned, about 8 minutes.
Stir in the onion, garlic, and five-spice powder. Cook, stirring occasionally, about 2 minutes.
Stir in the soy sauce, rice vinegar, and 1/4 cup of water. Use a wooden spoon to scrape the bottom of the pan to release any stuck on bits and bring to a boil.
Reduce heat to medium-low, cover the dutch oven and simmer for 45 minutes.
Make the rice while the pork simmers: Add the rice and 1 1/2 cups water to a medium-size saucepan. Stir and bring to a boil over medium-high heat. When water begins to boil place a lid on the pan and reduce the heat to low. Simmer the rice over low heat, WITHOUT REMOVING THE LID, for 10 minutes the turn off the heat and let the rice sit, WITHOUT REMOVING THE LID, for 15 more minutes.
Take the lid off the dutch oven and simmer uncovered until pork is tender and sauce thickens a bit, about 10 more minutes.
Take the lid off the rice and fluff with a fork. Serve the the pork over the steamed rice.