Wash the Hokkaido pumpkin, cut in half, scrape out the seeds, and cut the flesh into pieces no thicker than 1 cm.
Heat 2 tablespoons rapeseed oil in a large pan over medium-high heat. Add the minced beef and cook, breaking it apart, until browned, about 5 minutes. Chop the onion and add to the pan, then sauté until translucent, about 3 minutes. Crush the canned tomatoes and add with the tomato juice. Season to taste with salt, pepper, paprika powder, oregano, thyme, basil, and soy sauce, then add the granulated broth. Simmer for about 5 minutes.
Grease a baking dish. Layer the ingredients as follows: meat sauce on the bottom, then pumpkin pieces, then meat sauce, then cheese slices. Repeat this pattern until all ingredients are used, ending with a layer of cheese on top. Bake at 175°C (347°F) on the bottom rack for 50 minutes.