How to Make It
In a shallow glass or ceramic baking dish, rub the vinegar over the tenderloins. In a small bowl, combine the coriander with the peppercorns, salt, fennel seeds and cayenne. Rub half of the spice mixture on each tenderloin. Cover the tenderloins and refrigerate for at least 4 hours or overnight.
Preheat the oven to 400°. In a large skillet, heat the vegetable oil. Add the onion and cook over low heat, stirring occasionally, until softened but not browned, about 5 minutes. Add the bread crumbs and garlic and stir over moderately high heat until the crumbs are toasted and fragrant, about 3 minutes. Transfer the crumb mixture to a plate and let cool completely.
In a food processor, pulse the crumb mixture until even textured. Transfer the mixture to a large plate and toss it with a fork to break up any lumps; spread the crumbs in an even layer.
Roll the spiced pork tenderloins in the crumb mixture, pressing firmly to help the crumbs adhere all around. Transfer the tenderloins to a rack set on a rimmed baking sheet and bake for about 25 minutes, or until the crumb coating is crisp and browned on the outside and the meat is juicy and slightly pink on the inside. Let the pork stand for 5 minutes, then carve into thick slices and serve.