1 tablespoon fresh chopped oregano or 1 teaspoon dried oregano
Preheat oven to 350°F.
Cook noodles according to package directions; drain. Toss with 2 tablespoons oil and set aside.
In a medium skillet, cook and crumble sausage in 1 tablespoon olive oil over medium heat until browned and fully cooked; 7-10 minutes.
Add onion and garlic; cook and stir until tender; about 4 minutes.
Add marinara sauce to sausage mixture; set aside.
In a medium bowl, mix together the ricotta cheese, egg, ¼ cup Parmesan Cheese and chopped spinach; set aside.
In a greased 9x13-inch baking dish, spread 1 cup of sausage mixture on the bottom.
Top with 3 lasagna noodles. Spread ¼ of the ricotta cheese mixture on noodles; layer with 1 cup sausage mixture. Sprinkle ½ cup Italian cheese over mixture. Repeat this process three more times, starting with noodles and finish with remaining ¼ cup Parmesan cheese, sprinkle with oregano.