Tie together reserved cilantro stems with kitchen twine.
Heat oil in a medium pot over medium heat. Cook
onion and garlic, stirring occasionally, until tender, about
8 minutes. Add chili powder, and season with salt and
pepper; cook for 1 minute. Add rice, and stir to coat. Add
cilantro-stem bundle and the water; bring to a boil.
Reduce heat to low, and gently simmer, covered, until water
is absorbed, about 15 minutes.
Remove from heat, and add peas (do not mix). Cover, and
let stand for 10 minutes. Discard cilantro-stem bundle.
Season with salt and pepper. Stir in cilantro leaves.