Melt butter in a large skillet placed over medium-high heat. Add the onion and barley; cook, stirring frequently, until the onion begins to soften, about 5 minutes. Stir in the allspice, turmeric, curry powder, salt, and black pepper. Pour in the chicken broth, and bring to a simmer.
Cover skillet with lid, and reduce heat to low; simmer until the barley is tender, about 30 to 40 minutes. Fluff the pilaf with a fork, and gently stir in the slivered almonds and raisins.
