Prepare the pasta in boiling salted water according to the instructions on the packet. Grate 75 g cheese finely, dice the remaining cheese finely. Whisk sour cream and eggs, season with salt, pepper and nutmeg. Stir in grated cheese. Wash tomatoes, drain, quarter and remove seeds. Cut the tomatoes into small cubes. Cut soft tomatoes into strips. Clean and wash spring onions and cut into thin rings
Drain the pasta, rinse under cold water and drain well. Grease the springform pan well with a tube bottom insert (26 cm Ø). Close the outside of the tin tightly with aluminium foil. Line the edge and bottom of the mould with ham slices
Line the bottom of the springform pan with a thin layer of noodles, spread 1/3 of the spring onions, fresh and soft tomatoes, and the cheese cubes on top. Pour over with approx. 1/4 of the sand casting. Repeat this procedure twice more. At the end, pour the rest of the custard over the pasta. Bake the pasta cake immediately in the preheated oven, 2nd shelf from below (electric oven: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for 1-1 1/4 hours. If the surface becomes too dark, cover with aluminium foil
Wash the basil and shake dry. Finely chop the leaves of 4 stems. Whip the crème fraîche with the whisk of the hand mixer for about 5 minutes until creamy. Stir in pesto and chopped basil briefly, season with salt and pepper
Take the pasta cake out of the oven and carefully remove from the edge. Turn the cake out onto a plate and serve with the basil crème fraîche. Garnish with the rest of the basil