01 - Preheat the oven to 425°F (220°C).
02 - Pat the lamb racks dry with paper towels, then season generously on all sides with salt and freshly ground black pepper.
03 - In a small bowl, combine rosemary, thyme, parsley, minced garlic, lemon zest, and olive oil; stir thoroughly to blend flavors.
04 - Brush the meaty side of each lamb rack evenly with Dijon mustard.
05 - Press the herb mixture firmly over the mustard-coated surface of the lamb to create an even crust.
06 - Place the racks bone-side down on a roasting pan or rimmed baking sheet lined with aluminum foil.
07 - Roast in the preheated oven for 20 to 25 minutes until medium-rare, reaching an internal temperature of 130°F (54°C); adjust timing for desired doneness.
08 - Remove from oven and cover loosely with foil; let rest for 10 minutes to allow juices to redistribute.
09 - Slice between the bones and serve immediately.