Step 1: Prepare the White Sauce

1. Make the Roux: In a medium saucepan, melt the butter over medium heat. Once melted, whisk in the flour and cook for 1–2 minutes, stirring constantly, to remove the raw flour taste.
2. Add the Milk: Gradually pour in the milk while whisking to prevent lumps. Continue whisking and cook for 5–7 minutes, or until the sauce thickens to a smooth, creamy consistency.
3. Season the Sauce: Stir in the garlic powder, ground nutmeg, salt, and pepper. Taste and adjust seasoning as needed. Remove the béchamel sauce from the heat and set it aside.

Step 2: Prepare the Spinach

1. Sauté the Spinach: Heat 2 tablespoons of olive oil in a large skillet over medium heat. Add the fresh spinach and cook for 2–3 minutes, or until wilted. If using frozen spinach, ensure it’s thawed and fully drained before adding it to the skillet.
2. Season the Spinach: Sprinkle with a pinch of salt and pepper. Remove from the heat and let it cool slightly before layering.

Step 3: Cook the Lasagna Noodles

1. Boil the Noodles: If using traditional lasagna noodles, cook them in salted boiling water according to package instructions. Drain and lay them flat on a baking sheet to prevent sticking. If using oven-ready noodles, skip this step.

Step 4: Assemble the Lasagna

1. Preheat the Oven: Preheat your oven to 375°F (190°C).
2. Spread the Base Layer: Grease a 9×13-inch baking dish with cooking spray or olive oil. Spread a thin layer of the béchamel sauce on the bottom of the dish.
3. Layer the Ingredients:
   • Lay down a single layer of lasagna noodles.
   • Spread a layer of ricotta cheese evenly over the noodles.
   • Add a layer of sautéed spinach.
   • Drizzle 1–2 tablespoons of pesto over the spinach.
   • Sprinkle mozzarella and Parmesan cheese over the pesto.
   • Pour a thin layer of béchamel sauce over the cheese.
4. Repeat: Continue layering in the same order until all ingredients are used, finishing with a layer of béchamel sauce topped with mozzarella, Parmesan, and optional provolone cheese.

Step 5: Bake the Lasagna

1. Cover and Bake: Cover the dish with aluminum foil and bake for 35 minutes.
2. Uncover and Broil: Remove the foil and broil for an additional 5–10 minutes, or until the cheese on top is golden and bubbly. Keep a close eye to prevent burning.

Step 6: Rest and Serve

1. Let it Rest: Allow the lasagna to rest for 10–15 minutes before slicing. This helps the layers set and makes serving easier.
2. Garnish and Serve: Garnish with fresh basil leaves and additional Parmesan cheese. Serve hot and enjoy!