Peel the potatoes and pumpkin and cut into pieces. Season the pieces in a bowl with salt, pepper and thyme and mix thoroughly, then pour into a baking dish. Whisk the cream with half of the parmesan and pour over the potato and pumpkin pieces. Put the whole thing in the oven for 25 minutes at 180 °.
In the meantime, wash the tomatoes, remove the stalk and scratch the top in a cross shape. When the baking time is up, take the pan out of the oven, spread the tomatoes on top and sprinkle with the rest of the parmesan. Bake again for 25 minutes (the baking time may vary depending on the size of the pieces, it is best to try one piece).