Mix the spelt flour with the eggs, add 1 tablespoon of olive oil and a few tablespoons of water, as much is necessary to make a dough with the right consistency.
Wrap it in cling film and leave it to rest for half an hour.
Chop the celery, carrots, onion and garlic clove and fry them in a pan with 4 tablespoons of olive oil, then add the asparagus cut into rounds, leaving the tips 2-3 cm long.
Add the tomato puree and season with salt and pepper. Cook over a low heat for 30 minutes.
Prepare the béchamel: heat the milk with a pinch of salt; melt 25 g of butter in a small frying pan and add the flour; pour the resulting roux into the hot milk, beating with a whisk, and continue cooking, stirring with a wooden spoon, until it thickens.
Add a pinch of nutmeg and allow to cool.
Roll the pasta into thin sheets, cut them into pieces and boil the lasagne in lightly salted boiling water; drain and lay them on a tea towel to dry.
Grease an oven tray and arrange the lasagne by alternating layers of pasta, layers of vegetable sauce and layers of béchamel.
Spread the remaining béchamel and grated Parmesan over the top and bake at 200°C for 30 minutes.