• Preheat the oven to 375°F. Set out a 7x10x2-inch (or an 8x11x2-inch) dish.

Make the sunflower cheese

• Make the sunflower “cheese” sauce. In an upright, high speed blender, combine the drained sunflower seeds, water, nutritional yeast, garlic powder, onion powder, cumin, paprika, coriander, turmeric, lime juice, hot sauce, olive oil, salt, and pepper. Blend the sauce until completely smooth and silky. Check the sauce for seasoning and adjust if necessary. Set aside.

Sauté the sliced peppers

• Heat a large skillet over medium high heat. Pour in 1 tablespoon of the olive oil and swirl it around. Add all of the sliced peppers into the skillet at once. Season liberally with salt and pepper. Stir the peppers periodically until they are slightly softened, about 7-8 minutes. Remove the skillet from the heat and transfer the sliced bell peppers to a large bowl or plate.

Make the quinoa black bean filling

• Wipe out the skillet and return it to the stove over medium heat. Add the remaining olive oil to the skillet and swirl it around.
• Add the onions to the skillet and sauté until very soft and translucent, about 3-4 minutes. Add the garlic, cumin, coriander, paprika, and chili powder to the skillet and stir until spices are very fragrant, about 30 seconds. Then, add the tomato paste. Stir and cook out the tomato paste until it darkens in colour, about 30 seconds. Add the cherry tomatoes, corn kernels, and black beans to the skillet, and sauté for another 3 minutes, or until the cherry tomatoes start to break down a bit. Season liberally with salt and pepper.
• Add the quinoa to the skillet and stir to coat in the seasoning. Pour in the vegetable stock and give everything a stir. Bring the heat up to high and let the mixture boil for a minute or so. Then, lower the heat to a simmer, partially cover the skillet with a lid, and cook until almost all of the stock is absorbed and the little tails on the quinoa have started to pop out, about 15 minutes. The mixture should still be slightly wet, but definitely not fluid. If it is fluid, continue to simmer, uncovered, until excess liquid is absorbed. Once done, Remove the quinoa and black bean mixture from the heat. Stir in the lime juice.

Assemble and bake the casserole

• Spread the tomato sauce/salsa evenly across the bottom of your baking dish. Arrange ½ of the sautéed bell peppers on top of the salsa. Transfer all of the quinoa mixture on top of the bell peppers. Spread the quinoa mixture out evenly with a spatula. Pour all of the sunflower “cheese” sauce evenly over the top and spread it out over the surface. Top the casserole with the remaining sautéed bell peppers.
• Cover the casserole loosely with foil or an inverted baking dish. Slide the casserole into the oven and bake until totally heated through, about 25 minutes, removing the cover for the last 10 minutes. Switch the oven to broil and broil the top of the casserole for 2 minutes or so, or until the edges of the peppers are golden and there's slight browning on the sunflower "cheese." Definitely keep your eye on it the whole time during this stage! Once done, remove the casserole from the oven.
• Serve the casserole warm with diced ripe avocado, chopped fresh cilantro, toasted pumpkin seeds, and dabs of hot sauce if you like.