Add the olive oil to a large skillet over medium-high heat. Once the oil is hot, add the onions. Sauté for 5 minutes, until beginning to brown, then add the sausage. If the sausage is in a casing, remove from the casing before adding to the skillet. Break up the sausage with a wooden spoon as you sauté.
Once the meat is cooked through, add the garlic and red pepper flakes. Sauté for 1 minute, until fragrant. Stir in the tomato paste, followed by the water and canned tomatoes.
Finally, add the chopped fresh herbs, oregano, salt, and pepper. Stir to combine all the ingredients. Bring the ingredients to a lively simmer, then cover with a lid. Simmer for 20-25 minutes to allow the ingredients to marry and flavors to intensify.
Make the Ziti
While the sauce simmers, cook the pasta according to the directions. Drain and set aside. I drizzle and then toss pasta with a bit of olive oil to prevent the noodles from sticking to each other while waiting to assemble to the ziti.
Preheat the oven to 350F.
Spread a layer of the sauce on the bottom of a 9x13 baking dish. Spread half the ricotta cheese on top of the sauce, in dollops. Add the pasta, then add all the remaining sauce.
Add dollops of the remaining ricotta cheese over the top of the sauce, followed by the mozzarella cheese (I tear apart small pieces from the fresh mozzarella ball and sprinkle over the top of the sauce) and parmesan cheese.
Bake the ziti, uncovered for 20-25, until the sauce bubbles on the sides and the cheese melts. Turn off the oven and turn on the broiler. Broil the ziti for just a couple of minutes to brown the cheese. The broiler step is optional, but highly recommended. Top with extra fresh parsley or basil, if desired. Serve warm.
Notes
Tomatoes: I use Jovial brand tomatoes, which come in 18.3 ounce glass jars. This is why the recipe calls for this particular size. Most brands sell 14.5 ounce or 28 ounce size cans. If you're using a different brand, do your best to get about 34-36 ounces of tomatoes. The sauce recipe is adapted from The Defined Dish Cookbook. I highly recommend adding this cookbook to your collection, it's a good one!