Peel and halve shallot. Slice one half into very thin rounds and mince the other half. Slice thin rounds from pointed half of Fresno chile. Discard seeds if you prefer less spice. Stem and mince other half of Fresno chile. Zest lime, halve, and juice. Mince cilantro. Hold romaine head at root end and chop coarsely. Shuck corn, rinse, and carefully remove kernels from cob. On a separate cutting board, slice tenderloin into medallions, ½"-¾" thick. Season both sides with ¼ tsp. salt and a pinch of pepper.
Prepare the Mango
Remove mango ends and stand on one end. Peel with a peeler and cut along each side of pit, removing flesh. Cut half the flesh into ¼" dice and mash other half in a mixing bowl.
Make the Salsa
In another mixing bowl, combine diced mango (reserve mashed for vinaigrette), minced shallot (reserve rounds for salad), minced Fresno to taste (reserve rounds for garnish), 2 tsp. lime juice (reserve 1 tsp. for vinaigrette), and cilantro. Toss until thoroughly combined and set aside to let flavors marry.
Grill the Medallions
Heat outdoor grill or grill pan over medium heat. Coat grill with cooking spray. Grill pork until browned and reaches a minimum internal temperature of 145 degrees, 3-4 minutes per side.
Make the Salad
To the bowl with the mashed mango, combine 1 tsp. lime zest, 1 tsp. lime juice, 1 Tbsp. olive oil, and a pinch of salt and pepper. Add romaine, corn, shallot rounds (to taste), and pepitas to bowl with vinaigrette. Mix thoroughly. Season to taste with salt and pepper.
Finish the Dish
Place pork medallions on a plate and top with salsa. Serve salad alongside pork. Garnish with Fresno rounds to taste.