In a 10-inch cast iron or oven safe skillet, sauté onion in 1/2 Tbsp olive oil (as original recipe is written // adjust if altering batch size) over medium-low heat until soft – about 10 minutes – seasoning with a pinch of sea salt and black pepper. Set aside.
Preheat oven to 400 degrees F (204 C).
Add asparagus and squash to a mixing bowl and top with remaining 2 Tbsp olive oil, 3/4 tsp salt, pinch of black pepper, 1/4 tsp garlic powder (optional), and 2 Tbsp of the vegan parmesan cheese (amounts as original recipe is written // adjust if altering batch size). Toss to coat.
Top with an even layer of the vegan parmesan cheese (~3/4 cup // as original recipe is written // adjust if altering batch size) and bake at 400 degrees F (204 C) for 30 minutes. Then broil on high for the last 1-2 minutes to toast up the top (optional, but recommended). Watch closely as it can burn quickly. Let rest for a few minutes before serving.
*Parmesan recipe adapted from Veggieful
*Nutrition information is a rough estimate calculated with 3/4 cup nutritional yeast per 4 servings.