If you have a batch of this rice in your freezer, dinner's already halfway done.
In blender, puree first 4 ingredients, 1/2 tsp. salt, and 1/2 tsp. pepper. In saucepan, cook onion in oil over high, stirring often, until soft, 5 minutes. Stir in rice, garlic, and cilantro puree. Bring to simmer. Reduce heat to low; cover. Simmer until rice is almost tender, 18 minutes. Spread rice out on baking sheet. Let cool. Transfer to large container. Refrigerate rice.