Step 1
Preheat oven to 350 degrees F (175 degrees C). Spread pine nuts on a rimmed baking sheet.
Step 2
Toast pine nuts in the preheated oven tossing occasionally until golden brown 8 to 10 minutes. Let cool.
Step 3
Increase oven temperature to 450 degrees F (230 degrees C). Toss carrots with 1 tablespoon olive oil on a separate rimmed baking sheet; season with salt and pepper.
Step 4
Roast carrots in the preheated oven tossing occasionally until softened and browned 15 to 20 minutes.
Step 5
Heat 1 tablespoon oil in a large ovenproof skillet over medium-high heat. Season pork tenderloin with salt and pepper; cook in the hot oil turning occasionally until golden brown 10 to 15 minutes.
Step 6
Transfer skillet to the oven; roast pork until an instant-read thermometer inserted into the center reads at least 160 degrees F (71 degrees C) about 15 minutes.
Step 7
Combine pine nuts remaining 3 tablespoons olive oil and garlic in a food processor; process into a coarse paste. Add 1/4 of the carrots 1 tablespoon vinegar 1 tablespoon water and red pepper flakes. Process adding more water as needed into a coarse puree. Season with salt and pepper.
Step 8
Toss remaining carrots remaining 1 tablespoon vinegar and watercress in a large bowl. Season with salt and pepper.
Step 9
Slice pork and top with carrot puree; serve with salad.