Preheat the oven to 400℉. Line a baking sheet with unbleached parchment paper. Pat the cod dry with a paper towel and place the filets on the prepared baking sheet.
Drizzle the fish with 2 tablespoons of avocado oil, chopped garlic, zest of 1 lemon, and scatter the lemon slice around the fish. Season with salt and pepper to taste and place in the preheated oven and bake for 18-22 minutes depending on the thickness of the fish. Be careful not to overcook the cod.
While the fish is baking, cook the spinach and mushrooms.In a large skillet over medium heat, add the remaining 1 tbsp avocado oil, butter, and the smashed garlic clove.Add in the mushrooms and sauté for 5-7 minutes or until golden brown.
Once the mushrooms have browned, add in the chopped spinach and sauté just until wilted. Season with salt and pepper to taste.*Feel free to add a splash of cream to make the spinach and mushrooms for a little creaminess.
When the fish is done baking, remove it from the oven and serve it on a bed of spinach and mushrooms, then give it a good squeeze of lemon. Enjoy!