Peel and chop the onions. Rinse and drain the beans and corn. Clean, wash and chop the spring onions. Remove seeds from chilli, wash and chop finely. Peel and chop garlic
Heat the oil. Brown the vegetable onions in it. Add garlic, spring onions and chilli and steam for about 2 minutes. Add tomatoes with juice, ketchup, beans and corn. Let everything simmer for about 5 minutes. Season to taste with salt, pepper and sugar
Finely grate the cheese. Spread the bottom of a greased casserole dish (approx. 15 x 25 cm) with 2-3 tbsp. sour cream. Alternately layer lasagne dishes, vegetables and 2/3 cheese. Finish with vegetables. Spread the rest of the sour cream and cheese on top. Bake in a hot oven (electric cooker: 200 °C / convection oven: 175 °C / gas: level 3) for approx. 35 minutes