This is a primal-ish version of a nostalgic favorite of mine. My grandmother used to bring us to the farmer's market and buy those HUGE zuchinni. She would bake this with breadcrumbs, which of course is out of the question.
The cheats: hazelnut meal, cheese, crushed tomatoes
one large zuchinni (12"ish inches long)
one pound hot Italian sausage
around 2 cups crushed tomatoes (you can season this with salt and pepper, Italian herbs, and a little olive oil)
~1/2 cup hazelnut meal
1/2 lb cheese, cubed or shredded
Slice one large zuchinni lengthwise, salt, and butter all sides of it. Bake, cut-side-down, in your baking pan until it's mostly tender.
Meanwhile, cook around 1 pound of crumbled hot italian sausage (if you can't find a primal version of this in your grocery store, you should be able to find a good recipe that uses just herbs and spices in addition to the ground pork). Pour this into a bowl and add the crushed tomatoes along with any Italian herbs like snipped basil and oregano. Saute some sliced crimini or portabello mushrooms, onions, and garlic then add this mixture to the meat mixture. Add around 1/2 c hazelnut meal, and 1/2 lb cheese of your choice (in small cubes or shredded). Mix it all together.
When your zuchinni halves are tender, take them out of the oven and let them cool for a little while. Then scoop out the middle of each (you can compost this or eat it). Place each half in your baking pan, cut side up, and fill each with the meat filling that you've made. Optionally, you can spread more crushed tomatoes and/or shredded cheese on top. Bake at 350F until the zuchinni are very tender and the mixture is hot all the way through. This is even better as leftovers.