Fresh Spinach with Garlic-Yogurt Sauce

Heat 3 tablespoons oil in heavy large skillet over medium heat. Add onion and sauté until translucent, about 5 minutes. Add tomato paste; stir 1 minute. Add chiles and 1/3 of spinach. Cook until spinach wilts, adding remaining spinach in 2 additions and tossing often, about 4 minutes. Mix in rice. Cover and simmer until rice is tender and moisture from spinach is absorbed, adding water by tablespoonfuls if needed for rice, about 10 minutes. Uncover and continue to cook until mixture is dry, about 2 minutes; discard chiles. Meanwhile, press garlic cloves into small bowl, stir in yogurt, and season with salt and pepper. Melt butter with 1 tablespoon oil in small skillet. Mix in cayenne and remove from heat. Spread spinach mixture on platter; make indentations with back of spoon. Spoon yogurt into indentations and drizzle with cayenne butter.