In a medium saucepan, heat the oil. Sauté the onion in the oil for 5 minutes. Add in garlic, brown basmati rice, and saffron. Stir for about 2-3 minutes until you can smell the nuttiness of the brown basmati rice.
Stir in cayenne pepper, salt, and broth. Bring to a boil, reduce heat to a simmer, cover, and cook for about 25-35 minutes, until most of the broth has absorbed. Let stand for about 5 minutes before serving. Sprinkle with slivered almonds if using.