Preheat oven to 375 degrees Fahrenheit. Spray baking dish with oil spray. Place peppers in baking dish cut side up.
In a skillet over medium heat, add oil. Add onion and saute, approximately 3 minutes. Add garlic, salt, pepper, cumin, chili powder and cook for 1 minute. Add tomato and cook for 2 minutes.
Remove skillet from heat and mix in quinoa, beans, lime, and cilantro. Scoop one-quarter of the mixture into each pepper.
Place ½ cup water into baking dish then cover it tightly with foil.
Place baking dish into oven and cook for 40 minutes.
Remove and serve hot. Optional: garnish with toasted cashews.