Bring a large pot of salted water to a boil. Wash and dry all produce. Trim and quarter zucchini lengthwise; cut crosswise into ½-inch-thick pieces. Halve, peel, and dice onion. Mince garlic.

Heat a drizzle of olive oil in a large pan over medium-high heat. Add beef and season with half the Italian Seasoning (you’ll use the rest later), salt, and pepper. Cook, breaking up meat into pieces, until browned and cooked through, 4-6 minutes. Turn off heat. (TIP: If there’s excess grease in your pan, carefully pour it out.) Transfer beef to a plate.

Once water is boiling, add spaghetti to pot. Cook, stirring occasionally, until al dente, 9-11 minutes. Carefully reserve ½ cup pasta cooking water (¾ cup for 4 servings), then drain.

While spaghetti cooks, heat a drizzle of oil in pan used for beef over medium-high heat. Add zucchini and onion. Cook, stirring, until softened, 5-7 minutes. Stir in garlic and remaining Italian Seasoning; cook until garlic is fragrant, 30 seconds.

Add beef, tomatoes, stock concentrate, and reserved pasta cooking water to pan with veggies. Bring to a boil, then reduce heat and simmer until thick and saucy, 5-10 minutes. (TIP: If mixture begins to stick to the bottom of the pan, stir in a splash of water.) Taste and season with salt and pepper. Stir in 1 TBSP plain butter (2 TBSP for 4 servings) until melted.

Add spaghetti and garlic herb butter to pan with ragù; toss to combine. Divide pasta between plates. Sprinkle with Parmesan and as many chili flakes as you like. Serve.