Classic Beef Lasagna

Prepare the Meat Sauce:
Finely chop the onion.
Heat some vegetable oil in a large pan over medium heat.
Add the chopped onion and sauté until translucent.
Mince the garlic cloves and add to the pan, cooking until fragrant.
Add the minced meat to the pan and cook until browned.
Chop the celery stalks and tomatoes, then add them to the pan.
Season with salt, ground black pepper, and dried ground sweet paprika to taste.
Stir in the tomato sauce and let the mixture simmer for about 10-15 minutes until thickened.
Prepare the Béchamel Sauce:
In a separate saucepan, melt the butter over medium heat.
Add the flour and stir continuously to form a roux.
Gradually whisk in the milk, ensuring there are no lumps.
Season with salt and dried ground nutmeg to taste.
Cook, stirring constantly, until the sauce thickens.
Assemble the Lasagna:
Preheat your oven to 180°C (355°F).
In a baking dish, spread a thin layer of meat sauce on the bottom.
Place a layer of lasagne sheets over the meat sauce.