Roast squash in a 375°F oven for 50 minutes until tender or cut squash in half and place in a microwave dish with 1/2 inch of water, lightly covered with plastic wrap for 20 minutes on high until tender. cool. When cool, scoop flesh from squash halves leaving the shell intact for stuffing.
For the filling, heat oil in a large pan and sauté red onion, jalapeño chili and red pepper for 2 minutes. Add beans, corn and chili powder; sauté 1 minute longer. Add cooked squash, cilantro, lime juice and salt, cook 1 minute until heated through.
Fill squash halves with filling, mounding mixture in the center.