An Italian's family secret! He revealed this TRICK to me at an expensive restaurant on Christmas Day

Italian chef shared this secret with me at an upscale restaurant during a Christmas dinner, and now I want to share this delicious recipe with you, my viewers!
Juicy pork tenderloin with oranges and onions at the bottom is a fragrant dish made from tender pork, seasoned with spices and love. For the filling, slice an orange and garlic, seasoning them with salt and pepper. Tie the tenderloin to seal in the filling and infuse it with a fruity aroma.
The result is a juicy, flavorful dish with a zesty, aromatic center — perfect for impressing guests or enjoying a cozy Christmas dinner at home.

2.4 lbs pork loin (1.1 kg)
Salt
Black pepper
Paprika
1 orange (≈200–250 g)
1 onion (≈150 g)
3 garlic cloves (≈9–12 g)
Bake for 60 minutes at 400°F (200°C)
6 potatoes (≈900–1000 g)
Boil the potatoes
1 bell pepper (≈150 g)
1 cucumber (≈200 g)
1 tomato (≈120 g)
1 bunch parsley (≈30 g)
2 radishes (≈20–30 g)
Black pepper