How to Make It
Melt the butter in a medium saucepan. Add the onion and garlic and cook over moderately high heat, stirring occasionally, until translucent, about 4 minutes. Stir in the rice and saffron threads. Add 4 cups of water and 2 teaspoons salt and bring to a boil, stirring occasionally. Cover the pan, reduce the heat to low and cook until the rice is tender, about 20 minutes. Transfer the rice to a large bowl and let cool completely.
Meanwhile, roast the red and yellow bell peppers over a gas flame or under a broiler, turning occasionally, until charred all over. Transfer to a paper bag and let steam for 15 minutes. Remove the skin, seeds, cores and ribs and coarsely chop the peppers.
In a medium saucepan of boiling salted water, cook the asparagus until just tender, about 2 minutes. Drain, rinse with cold water and drain again. Add the asparagus to the rice with the chopped peppers.
In a small bowl, combine the lime juice, vinegar, honey and chipotles. Whisk in the olive oil and season with salt and pepper. Pour the dressing over the rice and toss to combine. Stir in the cilantro and serve.