Trim lamb loins, and set them aside. Mix the dry rub ingredients together in a bowl or cup. In a small bowl, rehydrate the red pepper flakes in the warmed veggie broth. While the pepper flakes rehydrate, add other marinade ingredients to a blender, and then add pepper flakes and broth mixture. Blend until it is well mixed.
Place the loins into a large Ziploc bag, and pour in the marinade. Carefully remove air from bag and seal it. Refrigerate this for 4-hours (or vacuum seal for 1 - 2 hours).
After marinating loins:
Pat the lamb dry and rub it lightly with vegetable oil. Sprinkle the rub mixture over the entire surface of the meat. Setup your frill to allow for both direct and indirect cooking. While the meat incorporates rub, preheat your grill to 350-degrees.
Place the loins over direct heat and grill for 3-4 minutes per side; until you have nice grill marks and color. Once the desired color is achieved, move the loins to the indirect heat zone. Cook 3 min per side, flip the meat, add the glaze, and cook 2 more min. Repeat this so that both sides are glazed nicely.
Add your jalapeño & lemon zest to the remaining glaze and mix it well. Drizzle the glaze and finishing mixture over the meat when it come off the grill, then let rest for 5-10 min. Slice lamb and dredge through juices that have formed on the cutting board on the way to the plate.