Step 1

Preheat the oven to 425°. Halve the zucchini lengthwise. Use a spoon to scoop out the interior of the zucchini (reserving the flesh), leaving about 1/4 inch thick border around the edges. Arrange the zucchini boats on a parchment-lined, rimmed baking sheet.

Step 2

Chop the reserved zucchini flesh and set aside. Heat 2 tablespoons of the oil in a large skillet over medium-high heat. Add the sausage and cook, stirring to break up the sausage, until browned and crumbly, about 6 minutes. Add the chopped zucchini flesh, red bell pepper, garlic, red pepper flakes, and salt. Cook until the vegetables have softened, about 5 minutes. Remove the skillet from the heat. Stir in the oregano, basil, and marinara. Let cool 5 minutes. Stir in the mozzarella and 1/4 cup of parmesan.

Step 3

Divide the filling mixture evenly among the zucchini shells. Stir together the panko breadcrumbs, remaining 1/4 cup parmesan, and remaining 1 tablespoon olive oil in a small bowl. Sprinkle evenly on top of each stuffed zucchini.

Step 4

Bake on the middle rack of the oven until the breadcrumbs are golden brown, cheese is melted and zucchini is tender, about 20 minutes. Top with additional chopped fresh herbs, if you like.