Preheat oven to 400°.
Cut 1 pork tenderloin in half lengthwise, cutting to, but not through, other side; open halves, laying the pork flat. Cut each half lengthwise, cutting to, but not through, other side; open halves, laying pork flat. Repeat the procedure with remaining tenderloin. Sprinkle inside of tenderloins with 1 tablespoon parsley, 1/2 teaspoon salt, black pepper, and minced garlic. Top each tenderloin with 6 dried plums and 2 tablespoons piquillo peppers. Roll up each pork tenderloin, jelly-roll fashion, starting at long side. Secure pork at 2-inch intervals with twine; dust with flour.
Heat oil in a large ovenproof nonstick skillet over medium-high heat. Add pork; cook 6 minutes on each side or until browned. Add the remaining 1 tablespoon of parsley, onion, peppercorns, unpeeled garlic, and bay leaf; sauté 2 minutes. Stir in broth, sherry, and cumin. Wrap the handle of pan with foil, and transfer pan to oven. Cover and bake at 400° for 25 minutes or until a thermometer registers 160° (slightly pink). Transfer pork to a platter; let stand 5 minutes. Cut pork into 3/4-inch-thick slices, and sprinkle with remaining 1/4 teaspoon salt. Remove whole garlic cloves; squeeze to extract pulp. Stir into pan juices (discard garlic skins and bay leaf). Serve pan juices with pork.