Preheat the Oven: Preheat your oven to 325°F (163°C).
Prepare the Spice Rub: In a small bowl, combine the fennel seeds, dill seeds, dried oregano, anise seed, lemon pepper (if using), kosher salt, Italian seasoning, black pepper, onion powder, garlic powder, and crushed red pepper.
Prepare the Pork Tenderloin: Pat the pork tenderloin dry with paper towels.
Rub the Pork: Rub the spice mixture evenly over the entire surface of the pork tenderloin.
Roll and Tie the Pork: Roll up the seasoned pork tenderloin tightly and secure it with kitchen twine at regular intervals.
Sear the Pork: Heat olive oil in a large oven-safe skillet or roasting pan over medium-high heat. Sear the pork on all sides until browned (about 4-5 minutes).
Add Chicken Stock: Pour chicken stock into the skillet or roasting pan.
Roast in the Oven: Place the skillet or roasting pan with the pork in the preheated oven. Roast for 45-60 minutes or until the internal temperature reaches 145°F (63°C).
Rest and Slice: Remove the porchetta from the oven, let it rest, and then carefully remove the kitchen twine. Slice the porchetta into thin rounds.
Serve: Serve the porchetta slices on a platter, drizzling any pan juices over the top.