Clean, wash and shake spinach dry. Peel and wash carrots and celery and cut into fine cubes. Peel and finely dice onion and garlic. Heat the oil and fry the minced meat for about 10 minutes, turning it well. After approx. 6 minutes add vegetable cubes and garlic. Stir in tomato paste and dust with flour
Add stock and tomatoes. Bring to the boil while stirring, chopping the tomatoes coarsely. Season to taste with herbs, salt, pepper and sugar. Simmer the sauce for about 10 minutes while stirring
Grease an ovenproof dish (approx. 30 x 20 x 5 cm). Spread some béchamel sauce thinly on the bottom of the dish. Place 4 lasagne plates on top. Spread about 1/4 of the minced sauce on top. Spread about 1/4 of the spinach on top. Put some béchamel sauce on top again and cover with 4 lasagne sheets. Repeat with 2 more layers of pasta. Spread the rest of the béchamel sauce on the last pasta layer. Grate parmesan and gouda. Wash and slice the tomato. Spread tomato slices and cheese on the lasagne. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for about 45 minutes until golden brown