Prepare the oven and dish. Preheat the oven to 375°F. Lightly grease a deep 9×13-inch baking dish. Set a rimmed baking sheet aside to place beneath the dish during baking.

Brown the sausage. Heat a large skillet or Dutch oven over medium-high heat. Add the smoked sausage and cook for 4–5 minutes, stirring occasionally, until browned. Remove with a slotted spoon. Leave approximately 1 tablespoon of rendered fat in the pan. Add a little olive oil only if the pan is dry.

Brown the beef. Add the ground beef, 2 teaspoons of the SPG, the Steak & Burger Seasoning, and smoked paprika. Cook for approximately 7–9 minutes, breaking the meat into medium-sized crumbles, until browned and cooked through. Drain excess grease, leaving a little in the pan.

Cook the vegetables. Add the onion and bell pepper. Cook for 4–5 minutes until beginning to soften. Stir in the garlic and cook for 30–60 seconds. Add the tomato paste and cook, stirring, for 1–2 minutes.

Simmer the sauce. Stir in the crushed tomatoes, tomato sauce, drained diced tomatoes, Worcestershire sauce, broth, Italian seasoning, basil, optional red pepper flakes, and brown sugar. Return the sausage to the pan. Bring to a light simmer, reduce the heat to low, and simmer uncovered for 20–25 minutes, stirring occasionally, until thick but spreadable. Taste and add some or all of the remaining 1 teaspoon SPG as needed. Add salt or black pepper only if needed.

Cook the noodles. While the sauce simmers, bring a large pot of salted water to a boil. Cook the noodles 1–2 minutes less than the package directions, until just shy of al dente. Drain well and lay flat on a lightly oiled sheet pan or parchment paper to prevent sticking.

Mix the ricotta filling. In a medium bowl, combine the ricotta, egg, 1 cup mozzarella, ½ cup Parmesan, parsley, ½ teaspoon SPG, and ½ teaspoon Italian seasoning. Mix until evenly combined. Divide into three portions.

Portion the sauce and assembly cheeses. Spread 1 cup of meat sauce over the bottom of the prepared baking dish. Divide the remaining sauce into four roughly equal portions. Keep the assembly cheeses separate from the cheese already mixed into the ricotta. Each of the four cheese layers will use ¾ cup mozzarella, ¼ cup cheddar, and ¼ cup Parmesan.

Build the first three layers. Lay 3 noodles over the sauce, trimming to fit if needed. Spread with one-third of the ricotta filling, one portion of meat sauce, ¾ cup mozzarella, ¼ cup cheddar, and ¼ cup Parmesan. Repeat this sequence twice more, using a total of 9 noodles and all the ricotta filling.

Finish the top. Add the last 3 noodles. Cover with the final portion of meat sauce, spreading it over all exposed noodles. Top with the remaining ¾ cup mozzarella, ¼ cup cheddar, and ¼ cup Parmesan. Leave room at the top of the dish for bubbling; use a second small dish for any overflow ingredients.

Bake covered, then uncovered. Loosely cover with foil, lightly greasing the underside if needed to keep the cheese from sticking. Place the dish on the rimmed baking sheet. Bake for 30 minutes. Remove the foil and bake for another 20–25 minutes, until bubbling around the edges, hot in the center, and lightly browned on top. The center should reach 165°F. If desired, broil for 1–2 minutes in a broiler-safe dish, watching closely.

Rest and serve. Let the lasagna rest for 20–25 minutes before slicing. Garnish with parsley, if desired, and serve.