Salt zucchini slices and let sit for 15–20 minutes; pat dry.
In a large bowl, mix zucchini, onion, garlic, tomatoes, olive oil, and pepper.
In a small bowl, whisk eggs, sour cream, half the parmesan, and cheddar.
Combine mixtures and layer in a greased baking dish.
Top with remaining parmesan and almond flour or breadcrumbs, and a drizzle of olive oil.
Bake 35–40 minutes until golden brown.
Rest 10 minutes before serving.
Notes
Note: the nutritional values are for the casserole made with almond and Parmesan crust rather than panko crumbs. If you use panko crumbs instead, then the carbs will be around 16g, and fats will go down to 12 as we skip the almond flour.