Preheat oven to 425 degrees. Bring a large pot of salted water to a boil. Wash and dry all produce. Core, deseed, and thinly slice bell pepper. Trim and thinly slice scallions, separating whites from greens. Thinly slice chili, removing seeds for less heat. Quarter lemon. Pat scallops dry with paper towels. Drizzle with olive oil; season all over with paprika, salt, and pepper.

Toss bell pepper on a baking sheet with a drizzle of olive oil, salt, and pepper. Place garlic cloves on a small piece of foil; drizzle with olive oil. Season with salt and pepper. Cinch into a packet; place on same sheet. Roast on top rack until bell pepper is lightly charred and garlic is softened, 15-20 minutes. Transfer roasted garlic to a cutting board.

Once water is boiling, add spaghetti to pot. Cook until al dente, 9-11 minutes. Reserve 1/2 cup pasta cooking water (1 cup for 4 servings), then drain and set aside. Reserve empty pot for use in step 5.

Meanwhile, halve chorizo lengthwise; thinly slice into half-moons. Heat a large drizzle of olive oil in a large pan over medium-high heat. Add chorizo and cook, stirring occasionally, until lightly browned, 2-3 minutes. Turn off heat. Using a slotted spoon, transfer chorizo to a plate, leaving as much oil in pan as possible (you’ll use in step 6). Gently mash roasted garlic on cutting board with a fork.

Heat a drizzle of olive oil in pot used for pasta over medium-high heat. Add scallions whites and mashed garlic; cook, stirring, until fragrant, 30 seconds. Stir in crushed tomatoes, stock concentrate, roasted bell pepper, 1 tsp sugar (2 tsp for 4), and 1/2 tsp salt (1 tsp for 4). Simmer until thickened, 2-3 minutes. Stir in spaghetti, chorizo, cream cheese, 1 TBSP butter (2 TBSP for 4), and half the Parmesan until combined. If needed, stir in splashes of reserved cooking water until pasta is coated in sauce. Turn off heat; cover.

Heat pan with chorizo oil over medium-high heat. Once oil is hot, add scallops; cook until browned and cooked through, 2-4 minutes per side (for 4, cook in batches, if needed). Check spaghetti; add a splash more remaining reserved pasta cooking water if needed. Divide pasta between plates; top with scallops, scallion greens, remaining Parmesan, and a pinch of chili if desired. Squeeze lemon juice over dish. Serve with any remaining lemon wedges on the side.