Preheat the oven to 400 degrees F.
Halve your acorn squash and scoop out the pulp and seeds from the middle, making a cavity for the stuffing later.
Place cut-side-down on a lined baking sheet. Rub both sides liberally with 1 tablespoon of olive oil and season with some salt. Bake in a preheated oven for 30 minutes or until the squash becomes slightly tender.
Meanwhile, heat the other tablespoon of oil in a large skillet over medium heat.
Add the onion, carrots, and celery to the hot oil. Cook, frequently stirring, for about 5 minutes until the veggies start to caramelize.
Next, add the garlic, dried herbs, and broth. Bring to a simmer and reduce for 2 minutes. Season to taste with the remaining salt.
Then, add the quinoa, apple, and spinach. Cook gently until the spinach begins to wilt, about 2 minutes, then turn off the heat.
In a small bowl, mix the breadcrumbs and herbs.
Flip your cooked acorn squash so that it is cut-side-up. Generously fill each half with the filling, creating a mound in the middle.
Top each mound with the breadcrumb mixture. Then, top each with 1 tablespoon of butter.
Place back into the 400-degree oven and cook for another 20-30 minutes until the filling is browned and the squash is very tender.
Serve as a main course or side dish.