Place rice in medium bowl and add enough water to cover by 2 inches; using hands, gently swish grains to release excess starch. Carefully pour off water, leaving rice in bowl. Repeat four to five times, until water runs almost clear. Using a colander or fine mesh strainer, drain water from rice; place colander over bowl and set aside.
Bring 3 1/4 cups water to boil, covered, in small saucepan over medium-high heat. Add salt and season with pepper; cover to keep hot. Meanwhile, heat 1 1/2 tablespoons butter in large saucepan over medium heat until foam begins to subside; add vermicelli and cook, stirring occasionally, until browned, about 3 minutes.
Remove to small bowl and set aside. Add remaining 1 1/2 tablespoons butter to pan and heat until foam begins to subside; add onion and sauté until softened but not browned, about 4 minutes. Add garlic, cumin, coriander, and allspice to sautéed onion; cook until fragrant, about 30 seconds longer.
Add vermicelli and rice and stir to coat grains with butter; cook until edges of rice grains begin to turn translucent, about 3 minutes. Stir hot seasoned water into rice; return to boil, then reduce heat to low, cover, and simmer until all liquid is absorbed, about 16-18 minutes. Off heat, remove lid, and place kitchen towel folded in half over saucepan; replace lid. Let stand 10 minutes; fluff rice with fork and serve.