Quick and Easy Gnocchi Lasagna

Name: Quick and Easy Gnocchi Lasagna
Ingredients: 1 pound gnocchi (gluten-free for gluten-free); 1 tablespoon olive oil; 8 ounces Italian sausage, casings removed; 1 small onion, diced; 3 cloves garlic, chopped; 1/2 teaspoon red pepper flakes (optional); 1/2 teaspoon ground fennel seeds (optional); 2 cups marinara sauce (link); 2 teaspoons balsamic vinegar (optional); 1 teaspoon oregano; salt and pepper to taste; 2 tablespoons basil, thinly sliced; 4 ounces ricotta; 1/4 cup parmigiano reggiano (parmesan cheese), grated; 1 cup mozzarella cheese, shredded; 1/2 teaspoon lemon zest