• Bring a large pot of salted water to a boil.
• Meanwhile, peel, then cut half the onion into 1/4-inch pieces (whole onion for 4 portions).
• Peel, then mince or grate garlic. 
• Roughly chop parsley.
• Roughly chop spinach.
• To the ricotta container, add half the garlic salt and 1/4 tsp (1/2 tsp) chili flakes. (TIP: Use less chilis for a milder dish and more chilis for a spicy dish.)
• Season with pepper, then stir to combine.

• Add rigatoni to the boiling water. Cook uncovered, stirring occasionally, until tender, 10-13 min.
• Reserve 1/4 cup (1/2 cup) pasta water, then drain rigatoni.
• Meanwhile, cut bacon strips in half crosswise. 
• Heat the pan over medium. When hot, add bacon. Cook for 5-7 min, flipping occasionally, until crispy.**
• Remove from heat. Using tongs, transfer bacon to a paper towel-lined plate. Set aside.
• Discard bacon fat from the pan. Carefully wipe the pan clean. Use the same pan to cook onions in step 3.

• Meanwhile, heat a medium oven-proof pan (large oven-proof pan for 4 portions) over medium.
• When the pan is hot, add 1 tbsp (2 tbsp) oil, then onions. Season with salt and pepper.
• Cook, stirring occasionally, until tender, 3-4 min.

• To the pan with onions, add garlic and remaining garlic salt, then season with pepper. Cook, stirring often, until fragrant, 30 sec. 
• Add crushed tomatoes, broth concentrate and 1/2 tsp (1 tsp) sugar. Bring to a simmer, then reduce heat to medium-low.
• Cook, stirring occasionally, until sauce thickens slightly, 5-8 min.

• To the pan with sauce, add rigatoni, spinach, reserved pasta water and half the mozzarella.
• Season with salt and pepper, to taste, then toss to combine. (NOTE: If you don't have an oven-proof pan, transfer to an 8x8-inch baking dish for 2 servings, or 9x13-inch baking dish for 4 servings.)
• Sprinkle with remaining mozzarella, then dollop seasoned ricotta over top.
• Broil in the middle of the oven until cheese is golden-brown, 3-5 min.

• Let rigatoni al forno cool, 5 min.
• Roughly chop bacon.
• Divide between plates.
• Sprinkle parsley over top.
• Sprinkle with remaining chili flakes, if desired.
• Sprinkle bacon over plated pasta.

If you've opted to add bacon, cut strips in half crosswise. Heat the pan over medium. When hot, add bacon. Cook for 5-7 min, flipping occasionally, until crispy.** Remove from heat. Using tongs, transfer bacon to a paper towel-lined plate. Set aside. Discard bacon fat from the pan. Carefully wipe the pan clean. Use the same pan to cook onions in step 3.  

Roughly chop bacon. Sprinkle bacon over plated pasta.