Cook the spaghetti until al dente according to the package instructions. Drain and set aside.
Prepare the Meat Sauce:
Cook the diced bacon in a large frying pan over medium heat until crispy. Remove and set aside.
In the same pan, sauté the chopped red onion and minced garlic until fragrant.
Add the minced beef and cook until browned.
Season with salt, black pepper, paprika, and oregano to taste.
Stir in the tomato sauce and cooked bacon. Let simmer for 5-7 minutes.
Prepare the Béchamel Sauce:
Melt butter in a saucepan over medium heat. Stir in the flour and cook, whisking constantly, for about 1 minute.
Gradually pour in the milk, whisking continuously to prevent lumps.
Cook the mixture, stirring constantly, until it thickens. Season with salt and black pepper to taste.
Assemble the Dish:
Preheat the oven to 180°C (355°F).
In a greased baking dish, layer half of the cooked spaghetti, followed by half of the meat sauce, and then a layer of béchamel sauce.
Repeat the layers, and top with grated mozzarella cheese.