Lie the potato flat and finely slice it without cutting through to the bottom. Brush it with the butter and place it in a 200C oven for 15 minutes.
During cooking, baste the potato in melted butter from time to time. When it is golden, remove from the oven and cool.
Insert the pieces of chopped vegetables in between the layers, alternating between the different colours. Baste in butter, sprinkle with cheese and return to the hot oven for a few more minutes.
Season and serve.