Preheat the oven to 375. Cut the squash open and remove the seeds. Place the squash in the oven and roast for 25-35 minutes until a spoon slides into the flesh, remove and cool slightly.
Pour the oil in a shallow dish and dip the tortillas on each side. Rub the oily tortillas on to each other until they are each evenly coated. Spread on a baking sheet and bake for about 10-15 minutes until crisp and lightly golden. Flip over half way through baking. Keep an eye on the tortillas, depending on their moisture content they could go from white to burnt fairly quickly.
Next, pour a splash of the oil in a skillet and sauté the onions until just starting to become golden and soft.
When the squash is just barely cool enough to handle, scoop it out and place in a food processor or blender. If you have a food mill that could work too.
Place the black beans in another bowl. Divide the following of each into the bowl of squash and the beans in the other bowl: the cumin, coriander, lime juice, and half of the cilantro minced up.
Toss each bowl of goodness separately.
Dollop the warm squash on top of each hot tortilla. Top with the black beans, caramelized onions, the remaining cilantro & arugula. Add any other of your favorite toppings such as cheese, sour cream, or salsas.