How to Make It
In a large bowl, whisk the orange juice, tomato paste, mustard, garlic, chile, sugar, paprika and Worcestershire. Add the pork, cover and refrigerate overnight. Bring to room temperature before grilling.
Light a grill or preheat a grill pan and oil the grate. Remove the pork from the marinade and season with salt and pepper. Reserve the marinade. Grill the pork over moderately high heat, turning, until charred and an instant-read thermometer inserted into the thickest part registers 135°, about 20 minutes. Transfer to a work surface and let rest for 10 minutes. Keep the grill on.
Meanwhile, brush the orange rounds with oil and grill, turning once, until charred, about 4 minutes. Transfer to the work surface with the pork.
Scrape the marinade into a saucepan and bring to a boil. Cook until heated through and reduced slightly, 2 to 3 minutes.
Cut the pork into thick slices and arrange on a platter with the grilled orange rounds. Drizzle with the sauce and garnish with parsley; serve.