Peel and finely dice the onion and garlic. Heat the oil in a pan and fry the onion and garlic for about 8 minutes at low heat. Leave to cool. Cook macaroni in plenty of boiling salted water for about 8 minutes. In the meantime wash and clean the zucchini and tomatoes.
Cut the zucchini into long, thin slices. Slice tomatoes in six. Pluck the thyme leaves from the stalks, wash, dab dry and chop finely. Drain macaroni, quench and let drain. Whisk eggs, milk, thyme and onion-garlic mixture. Season with salt, pepper and nutmeg. Grease 2 ovenproof casseroles (20 cm Ø). Layer 1/4 of each of the macaroni, zucchini and tomatoes, repeat the process. Pour egg milk into the casseroles.
Season with salt, pepper and nutmeg. Grease 2 ovenproof casseroles (20 cm Ø). Layer 1/4 of each of the macaroni, zucchini and tomatoes, repeat the process. Pour egg milk into the casseroles. Cook in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 45 minutes. Remove and let cool slightly before serving