How to Make It
In a saucepan, boil the orange juice over moderately high heat until reduced to 2 tablespoons, about 8 minutes. Let cool, then transfer to a blender.
Meanwhile, in a small dry skillet, toast the cumin seeds over moderate heat, shaking the pan occasionally, until fragrant, about 2 minutes. Grind the cumin in a mortar or spice grinder.
Add the cumin to the blender along with the cilantro and lemon juice and blend until smooth. With the blender on, add the canola oil in a thin, steady stream. Season with salt and cayenne.