Ingredients

• 1/2 stick (1/4 cup) unsalted butter
• 2 medium onions, finely chopped (2 cups)
• 2 large garlic cloves, finely chopped
• 1 tablespoon finely chopped peeled fresh ginger
• 3 tablespoons curry powder
• 2 teaspoons salt
• 1 teaspoon ground cumin
• 1/2 teaspoon cayenne
• 1 (3 1/2- to 4-pound) chicken, cut into 10 serving pieces
• 1 (14.5-ounce) can diced tomatoes
• 1/4 cup chopped fresh cilantro
• 3/4 cup cashews (1/4 pound)
• 3/4 cup plain whole-milk yogurt
• Accompaniment: cooked basmati or jasmine rice
• Garnish: chopped fresh cilantro

Instructions

1. Heat butter in a 5- to 6-quart wide heavy pot over moderately low heat until foam subsides, then cook onions, garlic, and ginger, stirring, until softened, about 5 minutes. Add curry powder, salt, cumin, and cayenne and cook, stirring, 2 minutes. Add chicken and cook, stirring to coat, 3 minutes. Add tomatoes, including juice, and cilantro and bring to a simmer, then cover and simmer gently, stirring occasionally, until chicken is cooked through, about 40 minutes. (If making ahead, see cooks' note, below.)
2. Pulse cashews in a food processor or electric coffee/spice grinder until very finely ground, then add to curry along with yogurt and simmer gently, uncovered, stirring, until sauce is thickened, about 5 minutes.