Slow Cooker Stuffed Zucchini

Step 1
Scoop out flesh from the zucchini halves, leaving shells about 1/8 inch thick. (Zucchini flesh may be saved for another use.)

Step 2
Place tomatoes, 1/4 cup olive oil, salt, black pepper, garlic, basil leaves, Italian herb seasoning, and sugar into a food processor and pulse until blended, about 1 minute. Set mixture aside.

Step 3
Heat 3 tablespoons olive oil in a large skillet over medium heat; cook and stir onion until translucent, about 5 minutes. Add sausage to skillet and cook, stirring often, until browned and crumbly, about 10 minutes. Stir in the tomato mixture and heat until simmering; stir in Parmesan cheese.

Step 4
Place hollowed-out zucchini shells into the bottom of a large slow cooker, trimming them to fit if necessary. Spoon the sausage mixture into the shells, cover the cooker, and cook on High until tender, about 6 hours. Remove cover and spread a layer of mozzarella cheese over each stuffed zucchini. Cover and cook on High until cheese has melted, about 10 more minutes.