Place the sundried tomatoes in a dish and cover with water. Let these soak to soften a bit while you continue with the recipe.
Cook the Italian sausage and onion together in a large skillet until the sausage is browned and the onion is tender.
Using a slotted spoon, scoop the sausage and onion to a dish and set it aside.
Removed any excessive grease from the skillet.
Cut the ends from the zucchini and then cut them in half lengthwise. Set aside one half of a zucchini. The remaining zucchini halves, cut into 1/2 inch slices. Cut the reserved half into thin, long slices. Set the long slices aside for now.
Add the chopped zucchini to your skillet, along with 1/4 cup of water. Cover the skillet with a lid and simmer for about 10-15 minutes, or until just tender.
Meanwhile, whisk the eggs in a mixing bowl.
Drain the tomatoes and give them a quick rough chop. Add to the eggs.
Dice the mozzarella and add it to the mixing bowl.
Using a slotted spoon, scoop the zucchini out onto a cutting board and allow it to cool a few minutes.
Add the Italian sausage and onion to the mixing bowl.
Give the cooked zucchini a rough chop and add it to the mixing bowl.
Add in the garlic, 1/4 c parmesan cheese, salt, pepper, and Italian seasoning. Stir to combine all of the ingredients.
Spread the mixture into a lightly oiled square (9x9) baking pan.
Sprinkle the bread crumbs (see note below) and remaining parmesan cheese all over the top.
Arrange the long zucchini slices on top. It's okay if you don't use them all.
Bake for 40 minutes.
Enjoy!
Notes
Store bought bread crumbs can be very dry. I simply toast a slice of bread, let it cool to room temperature and then pulse it in a food processor. If you use store bought bread crumbs, I would recommend mixing them with a tablespoon of melted butter before sprinkling them on the casserole.
For low carb, you can omit the bread crumb topping.