Preheat the oven to 350 degrees F (175 degrees C). Lightly grease a medium casserole dish.
In a steamer basket over boiling water, steam the squash 10 minutes, or until tender. Remove from heat, and mash with a fork.
In a medium bowl, blend the eggs and heavy cream. Mix in the squash, 3/4 of the green onions, green bell pepper, dry stuffing mix, and Parmesan cheese. Season with salt and pepper. Transfer to the prepared casserole dish. Press the rosemary sprig into the center of the mixture. Top with feta cheese, tomato slices, and remaining green onions. Season with pepper.
Bake 45 minutes in the preheated oven, until lightly browned. Discard rosemary sprig before serving.