Preheat the oven:
Preheat your oven to 180°C (350°F). Grease a medium-sized rectangular baking dish.

Make the vegetable filling:
Heat olive oil in a pan over medium heat. Add onion and garlic, and sauté for 2–3 minutes until soft. Add zucchini, red pepper, mushrooms, and carrot. Cook for 5–7 minutes until vegetables are tender. Stir in spinach and cook until wilted.

Add chopped tomatoes, tomato paste, oregano, chili flakes, salt, and pepper. Simmer for 10 minutes until thickened. Set aside.

Make the cheese sauce:
In a saucepan, melt the butter over medium heat. Stir in the flour and cook for 1 minute. Gradually whisk in the milk to avoid lumps. Stir continuously until the sauce thickens. Remove from heat and stir in the cheddar cheese. Season with salt and pepper.

Assemble the lasagna:
Spread a spoonful of vegetable filling on the bottom of the baking dish. Layer with lasagna sheets, more vegetable filling, then a layer of cheese sauce. Repeat layers until all ingredients are used, ending with cheese sauce on top.

Top with cheese:
Sprinkle the mozzarella and parmesan evenly over the top.

Bake the lasagna:
Bake in the preheated oven for 30–40 minutes, or until golden and bubbly on top. Let it rest for 10 minutes before slicing.

Serve and enjoy:
Cut into portions and serve warm with a side salad or garlic bread.

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