Preheat the Oven: Heat your oven to 400°F. Grease a 9-inch springform pan and line with parchment paper, ensuring the edges overhang.
Prepare the Squash: Use a mandoline to slice the butternut squash into thin, uniform pieces for even cooking.
Make the Sauce: In a small frying pan, heat olive oil over medium heat. Sauté garlic until fragrant (about 1 minute). Stir in tomato paste, cumin, coriander, and chili flakes, cooking for another minute. Transfer to a blender with roasted red peppers, sugar, salt, and pepper. Blend until smooth.
Combine Ingredients: In a large bowl, toss the squash slices, broken lasagna noodles, spinach, basil, feta, Parmesan, and red pepper sauce. Mix thoroughly to coat.
Assemble the Lasagna: Layer the mixture into the prepared springform pan, pressing firmly after each layer. Wrap the top tightly with aluminum foil.
Bake the Lasagna: Place the pan on a baking sheet and bake for 1 hour. Meanwhile, prepare the béchamel sauce.
Prepare the Béchamel: Melt butter in a saucepan over medium heat. Whisk in flour and cook for 2 minutes. Gradually add milk, whisking constantly until smooth. Add Parmesan and garlic, stirring until thickened.
Final Bake: Remove foil from the lasagna. Spread the béchamel evenly on top. Increase oven temperature to 450°F and bake for another 15 to 20 minutes until golden brown.
Cool and Serve: Allow the lasagna to cool for at least 15 minutes before removing it from the pan. Slice and serve warm or at room temperature.