Heat the extra virgin olive oil in a large pot over medium-high heat. Once hot, add the onion and cook, stirring occasionally, for 6–8 minutes.

Add the butter to the pot. Once melted, add the garlic and cook for 1 minute until fragrant.

Add the tomato paste and mash it into the onion and garlic. Cook for 4–5 minutes until it deepens in color.

Add the crushed tomatoes, sugar, crushed red pepper, and basil sprigs. Season liberally with salt and pepper. Bring to a boil and then reduce heat to low. Simmer, covered, for 30 minutes. Remove the lid and continue simmering for at least 1 hour, uncovered, until the sauce is thick and jammy. Taste and season to your preferences, and discard the basil sprigs.

If using fresh spinach*, heat 1 teaspoon extra virgin olive oil in a large skillet. Once hot, add the spinach and ¼ cup of water. Cook, turning regularly, until the spinach wilts completely. Season lightly with salt and pepper.

Place the spinach on a paper towel-lined plate in an even layer. Transfer to the freezer for 5–10 minutes. Once the spinach is cool enough to handle, squeeze out all of the excess moisture and then roughly chop. Set aside.

Mix the ricotta, mozzarella, eggs, basil, lemon juice, and salt and pepper in a large bowl. Mix with a spoon until smooth.

Add the chopped spinach and stir until combined. Taste and season with salt and pepper. Refrigerate until needed.

If parboiling the manicotti, bring a large pot of salted water to a boil first. Add the manicotti and cook for precisely 5 minutes. Drain and rinse until cold water. Set aside.

Preheat oven to 350ºF.

Add half the pasta sauce to the bottom of a 9”x13” baking dish and smooth it into an even layer. Set aside.

Stuff the manicotti with the filling using a long spoon or a piping bag. Be sure each piece of pasta is fully stuffed, but be careful not to overstuff as it will split the pasta. Place the stuffed manicotti into the baking dish on top of the sauce. Continue on until all of the manicotti are stuffed.

Spoon 1–2 cups more sauce on top of the manicotti and smooth into an even layer. Sprinkle the remaining ½ cup mozzarella on top of the manicotti.

Cover the baking dish with foil and transfer it to the oven. Bake, covered, for 40 minutes. Remove the foil and bake for an additional 5 minutes.

Turn on the broiler and broil for 1–3 minutes until the cheese is browned and bubbly. Remove from the oven and let stand for 5–10 minutes.

Scatter a few fresh basil leaves on top of the casserole. Serve the manicotti with any remaining pasta sauce. Enjoy!