In a large oven safe skillet, such as cast iron, cook the zucchini and lemon juice over medium heat until the zucchini has softened, about 20 minutes. Drain excess liquid from the skillet, if needed.
Stir in the sweetener, cinnamon, and nutmeg to coat the zucchini.
Add the almond flour, melted butter, sweetener, and cinnamon to a small bowl and stir well to form moist crumbs.
Sprinkle the topping over the zucchini. Bake for 20 minutes. Let set for 10 minutes before serving.