Prepare the pork: Put coriander, fennel, and cumin in an 8" skillet over medium heat and cook, swirling pan occasionally, until seeds are toasted, about 5 minutes. Coarsely grind seeds in a spice grinder and transfer to a small bowl. Add paprika, sugar, and garlic and stir to combine. Put pork on a plate and season generously with salt. Rub pork with coriander mixture and cover with plastic wrap. Let sit at room temperature for at least 1 hour or refrigerate overnight.
Roast the vegetables: Heat oven to 475°. Put sweet potatoes on a baking sheet and bake, turning once, until tender, 40 to 50 minutes. Transfer to a plate; set aside. Increase heat to broil and arrange a rack 4" from heating element. Put tomatillos and poblanos on baking sheet and drizzle with 2 tbsp. olive oil. Broil, turning once, until charred and tender, about 10 minutes. Transfer tomatillos to plate with sweet potatoes and transfer poblanos to a bowl. Cover bowl with plastic wrap and set aside for 15 minutes. Peel poblanos, discarding seeds and stems, and tear poblanos into 1⁄2"-wide strips; set aside.
Heat remaining olive oil in a 12" skillet over medium heat. Add garlic and cook, turning occasionally, until golden brown, about 5 minutes. Increase heat to medium-high and add broccoli rabe; cook, stirring occasionally, until hot, about 3 minutes. Season with salt and remove pan from heat; set aside.
Reduce oven to 350°. Heat canola oil in a 12" cast-iron skillet over medium-high heat. Add pork and cook, turning, until browned on all sides, about 4 minutes. Place shallots cut side down under pork. Transfer skillet to oven and cook until an instant-read thermometer inserted into thickest part of pork reads 125°, 30 to 50 minutes. Transfer pork and shallots to a cutting board and let rest for 15 minutes. To serve, slice pork thinly and transfer to a platter along with shallots. Cut sweet potatoes into small pieces and halve tomatillos. Transfer potatoes, tomatillos, poblanos, and broccoli rabe to platter. Spoon Cilantro Mojo over pork.