Preheat oven to 375 F. Set a large (8.5 x 11 in. or similar size) oven-safe dish aside, or if you have a large oven-safe skillet (my 10” by 3” shown above works perfectly), you can use that to both sauté and bake.
Bring quinoa and broth/water to a boil in a medium sauce pan. Once boiling, reduce heat to low and cover with a tight-fitting lid; set a timer for 12 mins.
Meanwhile, prepare peppers and onion: chop bell peppers into bite-sized pieces (remove the stem and seeds), dice the jalapeño (remove the seeds, and also scrape out the ribs for less heat), and peel and chop the onion.
Heat 1 tbsp olive oil in a large skillet over medium-high heat. Add all of the peppers and onion; stir to coat with oil. Sauté without stirring for 5-7 mins, or until the bottom pieces start to become charred. Add the garlic, if using, and saute for 1-2 more mins. Add half of the chili powder (½ tbsp) and stir for 30 seconds. Remove from heat.
When the quinoa timer goes off: Check to see if the liquid has been absorbed and the outer layer (germ) has separated from the seeds. If neither has happened, replace the lid and continue cooking, checking about every minute. If it looks like all of the germs have separated, it’s done; if there’s some remaining liquid, you can steam it for a couple mins with the lid on and the heat off.
If you’re using a separate baking dish, move the sautéed veggies from the skillet to a large mixing bowl. (Or you can carefully mix everything right in whichever pan/dish is going in the oven to save yourself a dish to wash!). Add the quinoa, frozen corn, spinach, salsa, drained and rinsed beans, half of the cheese (1/2 cup), and remaining chili powder; stir to combine. Give it a try and add salt, pepper, more chili powder, etc. to taste (I added some freshly ground pepper and a bit of cayenne). Sprinkle remaining cheese on top.
Bake at 375 F for 10-15 minutes, or until cheese on top is melted. Meanwhile, prepare any toppings/sides. Serve right away, or you can shut the oven off and let it coast to keep it warm for a bit. Leftovers keep well in the fridge for about a week or freezer for a month (caveat: I'm personally not a fan of the texture fresh spinach gets when it's frozen and defrosted, so I prefer to add it in later).
Notes
*I like chunky salsa but use whatever kind you prefer.**Pre-shredded cheese works but I recommend shredding it yourself (see note above). Also, 1 cup is a modest amount for this size dish so feel free to add more.For more info on my organic suggestions, see my produce guide.