Preheat oven to 350ºF. Spray a medium baking dish with nonstick cooking spray and set aside.

In an extra-large sauté pan over medium heat, add olive oil and cook onions until translucent (5 minutes). Stir in spinach and garlic and cook until spinach has wilted.

Add flour, stirring for one minute. Stir in milk and cheese, stirring constantly until mixture begins to boil and thicken.

Add lemon zest. Season to taste. Fold in pasta and pour mixture into the prepared baking dish.

Bake until browned and bubbly (30-40 minutes).

Remove from oven and allow to rest while shrimp are baking.

Prepare popcorn shrimp according to directions on the box. Add hot cooked popcorn shrimp to top of the baked pasta and serve.