Preheat oven to 350°F. Bring a large pot of salted water to a boil and cook ziti pasta to al dente according to package directions. Drain and set aside.
Heat olive oil in a large skillet over medium-high heat. Add ground Italian sausage and cook, breaking into crumbles. When halfway cooked, add diced onions and cook until sausage is browned and onions are tender. Add minced garlic and cook for 30 seconds until fragrant.
Stir in tomato sauce, petite diced tomatoes, 1 teaspoon salt, ½ teaspoon pepper, ¼ teaspoon red pepper flakes, 1 teaspoon dried basil, and ½ teaspoon dried oregano. Reduce heat to low and simmer for 20 to 30 minutes, stirring occasionally.
For the Ricotta Mixture: In a medium bowl, combine ricotta cheese, grated Parmesan, grated Asiago, 1½ cups shredded mozzarella, ¼ teaspoon salt, and ¼ teaspoon pepper until smooth and well blended.
Remove meat sauce from heat. In a large bowl (or your pot), stir together the cooked ziti, warm meat sauce, and ricotta cheese mixture until fully combined.
Transfer pasta mixture into a 9x13 baking dish. Top with the remaining 1 cup of shredded mozzarella cheese.
Bake uncovered at 350°F for 30 minutes until hot and bubbling. Turn oven to broil for 2 to 3 minutes to lightly brown the melted cheese on top. Garnish with fresh basil if desired. Enjoy!