For the marinade, prick the rack of lamb 6 times with a sharp knife, making 1/2-inch deep incisions. Mix together all the marinade ingredients in a large bowl and then empty into a large plastic bag. Add the rack of lamb and press out as much as as possible from the bag before sealing and refrigerating for at least 4 hours or overnight.

Preheat the oven to 475 degrees Fahrenheit. Mix together the salt, rosemary, garlic powder, and pepper in a small bowl, then coat the rack of lamb in the mixture. Place it on a baking sheet along with the tomatoes, garlic, and shallots. Roast in the oven until desired doneness is reached, about for 10 minutes for rare, 15 minutes for medium rare.

To prepare the pesto, blend the fennel, pistachios, mint, basil, salt, and red pepper flakes together in a blender or food processor until smooth. While the blender is on, slowly add the olive oil in a thin and steady stream through the hole in the cap. Allow the mixture to continue to blend for 10 more seconds or until thick and smooth. Serve alongside the roasted lamb and tomatoes.