01 - Preheat the oven to 375°F.
02 - Heat 2 tablespoons of olive oil in a large oven-safe skillet over medium heat. Add chopped onion and minced garlic, sauté for 3 minutes until softened.
03 - Add diced butternut squash, sliced carrots, and sliced parsnips to the skillet. Cook, stirring occasionally, for 5 minutes.
04 - Stir in rinsed lentils, quinoa, dried thyme, dried rosemary, ground cumin, smoked paprika, salt, and black pepper. Pour in the vegetable broth and bring to a simmer.
05 - Cover the dish with a lid or foil and transfer it to the preheated oven. Bake for 35 minutes.
06 - Remove the dish from the oven, uncover, and stir in baby spinach leaves and lemon juice.
07 - In a small bowl, combine gluten-free breadcrumbs, nutritional yeast, and 1 tablespoon olive oil. Sprinkle this mixture evenly over the casserole.
08 - Return the casserole to the oven uncovered and bake for an additional 10 to 12 minutes until the topping turns golden and crisp.
09 - Allow the casserole to rest for 5 minutes before serving.