Wash and peel the asparagus and cut off the woody ends. Cut the asparagus into pieces about 5 cm long. Simmer asparagus skins and ends in 1 l boiling salted water with 1 tsp. sugar for about 15 minutes. Drain and collect the stock.
Wash tomato, carve crosswise and blanch with boiling water. Finely dice the tomato. Wash thyme, shake dry, pluck off leaves.
Heat the oil in a frying pan. Fry the asparagus and tomato for about 2 minutes. Deglaze with wine. Let it simmer down almost completely at medium heat.
Add spaghetti and so much asparagus stock (approx. 2⁄3 ) that all spaghetti is covered. From now on, always shake the roaster a little bit, so that everything is moving a little. Bring to the boil and simmer for about 10 minutes.
Always add so much of the remaining stock that all ingredients in the roaster are covered with enough liquid.
Grate parmesan. Season spaghetti with salt and pepper. Stir in butter and 100 g parmesan. Sprinkle with thyme. Add the rest of the parmesan.