Quarter the fennel bulbs and cut out the base of the stalk, setting aside the green fennel tops. Blanch the fennel in salted water for 3 minutes, then rinse with cold water and drain.
Cut the tomatoes crosswise and scald them in boiling water for 1-2 minutes, then peel off the skin and cut into small cubes.
Cut the onion into fine rings and sauté in some oil (preferably the oil from the sun-dried tomatoes) over medium heat until translucent, about 3-4 minutes. Chop the sun-dried tomatoes and add them to the onions along with the fennel, then fry over medium heat for 5 minutes.
Add the tomato paste and paprika powder and toast for 1-2 minutes. Add the fresh tomatoes, deglaze with the broth, and simmer over medium heat for 3-5 minutes to reduce slightly. Season to taste with marjoram, the reserved fennel greens, salt, pepper, and a pinch of sugar.
Preheat the oven to 200 °C (392 °F). Transfer the fennel mixture to a baking dish, sprinkle with breadcrumbs, and grate Parmesan over the top. Bake for 15-20 minutes until golden.
Serve as a vegetarian main course with fresh bread, or as a side dish with roasted meat.