First, combine marinade ingredients in a medium bowl and whisk to combine. (this will be fairly thick) Place pork cubes in a large Ziploc bag and pour marinade over meat. Seal bag well and place on a plate or mixing bowl (in case of leakage) in the refrigerator for several hours or preferably overnight.
When ready to cook, heat oil over medium heat in a large, heavy-bottomed saucepan or iron skillet. Add onions and fry, stirring often, to a light golden brown color. Add the pork and continue sautéing, stirring often, until meat is browned.
Stir in 2 tablespoons reserved marinade, chicken broth, and tomato sauce. Bring to a boil, then reduce to a simmer and continue cooking for about 15 minutes, stirring occasionally.
After 15 minutes, stir in uncooked potatoes and continue simmering an additional 15 minutes or until the meat is cooked through. (You may cover the saucepan with a tight fitting lid and place in a 350 degree oven for about 30 to 45 minutes at this point, if you prefer.)
Season with salt and pepper, to taste and serve warm.