Pork Tenderloin in a Sweet Citrus Sauce without wine

2 tablespoons unsalted butter 2 large vidalia onions or 2 large other sweet onions , sliced 2 tablespoons firmly packed dark brown sugar 2 tablespoons[...]

1/2 teaspoon salt 1/4 teaspoon ground cinnamon 1/4 teaspoon ground cardamom 1/8 teaspoon black pepper 1 large sweet potato , in 1-inch slices (peeled or not)[...]

1 cup orange juice 1/4 cup lime juice 4 tablespoons apple cider vinegar 1 cup piloncillo, grated (or brown sugar) 5 teaspoons garlic cloves , minced 1/2[...]