Ingredients

• 1/2 stick (1/4 cup) unsalted butter
• 3/4 cup farinha de mandioca* (manioc flour; not toasted)
• 1 1/2 cups chopped onion
• 5 garlic cloves
• 7 bottled red malagueta peppers**
• 1 teaspoon sugar
• 1 teaspoon cider vinegar
• 1 tablespoon plus 1/2 teaspoon salt
• 3 tablespoons olive oil
• 3 (1 1/2-pound) frenched racks of lamb (8 ribs each), trimmed of all but a thin layer of fat
• 3 tablespoons finely chopped fresh flat-leaf parsley
• *A coarse, granular meal made from grated cassava root, farinha de mandioca is available at some Latino markets and Sendexnet (866-736-3396; sendexnet.com).
• **Fresh malaguetas are difficult to find in the U.S.; instead, look for them bottled in vinegar or in the clear, strong brandy called cachaça, available at some Latino markets and Sendexnet (866-736-3396; sendexnet.com).
• an instant-read thermometer

Instructions

1. Put oven rack in middle position and preheat oven to 400°F.
2. Heat butter in a 10-inch heavy skillet over moderate heat until foam subsides, then cook flour, stirring, until golden brown, 3 to 4 minutes. Transfer to a small bowl.
3. Purée onion, garlic, peppers, sugar, vinegar, and 1/2 teaspoon salt in a blender until smooth, adding 1 to 2 tablespoons water if needed to facilitate puréeing.
4. Heat 2 tablespoons oil in a large nonstick skillet over moderate heat until hot but not smoking, then cook purée, stirring, until thickened, 3 to 4 minutes. (Don't worry if mixture turns blue-green; this sometimes results from the interaction of vinegar and immature garlic.) Reserve 5 tablespoons purée in a small bowl (for coating lamb) and transfer remainder to another small bowl (to be served on the side with lamb).
5. Sprinkle lamb with remaining tablespoon salt. Heat remaining tablespoon oil in cleaned 10-inch skillet over moderately high heat until hot but not smoking, then brown lamb 1 rack at a time, turning over once, about 4 minutes per rack. Transfer racks to a large roasting pan, arranging with bones curving downward.
6. Spread 1 1/2 tablespoons malagueta purée over meaty part of each rack of lamb, excluding ends. Stir parsley into farofa mixture, then pat mixture onto lamb (over purée) to coat, pressing gently to adhere.
7. Roast lamb until thermometer inserted diagonally 2 inches into center (do not touch bone) registers 125°F (for medium-rare), 20 to 25 minutes. Transfer to a cutting board and let racks stand 15 minutes (internal temperature will rise to about 130°F).
8. Cut each rack into chops and serve remaining purée on the side.