Step 1

Combine soy sauce, orange juice, maple syrup, and sesame oil in a large resealable plastic bag. Add tenderloin; close bag, pressing out air. Chill, turning once, 4–12 hours. Remove tenderloin from marinade and pat dry; discard marinade. Season lightly with salt.

Step 2

Preheat oven to 250°. Heat grapeseed oil in a large ovenproof skillet over medium-high. Cook tenderloin, turning occasionally, until browned on all sides, about 5 minutes. Transfer to oven and roast until an instant-read thermometer inserted into the thickest part of tenderloin registers 130°, 20–25 minutes. Transfer to a cutting board; let rest at least 10 minutes before slicing.

Step 3

While meat is cooking, heat 1 Tbsp. oil in a large saucepan over medium. Cook shallot and garlic, stirring often, until softened, about 3 minutes. Add curry paste and lime zest and cook, stirring constantly, until paste is slightly darkened in color and very fragrant, about 4 minutes. Add coconut milk, bring to a simmer, and cook until reduced by half, 20–25 minutes. Let curry mixture cool.

Step 4

Transfer curry mixture to a blender and add agave, lime juice, ¼ cup cilantro, and 2 Tbsp. water; blend until very smooth. With motor running, add remaining ½ cup oil in a steady stream; blend until sauce is thick and emulsified. Transfer to a small saucepan and heat over medium just until warmed through.

Step 5

Serve pork over sauce topped with cilantro and pumpkin seeds.

Step 6

Do Ahead: Sauce can be made 1 day ahead. Cover and chill.