Prep the oven and pan: Preheat to 400°F (200°C). Lightly grease a large baking dish with oil.

Hollow the zucchini: Trim ends and slice each zucchini lengthwise. Use a spoon to scoop out the centers, leaving a 1/4-inch shell. Save about half the scooped flesh, chop it, and set aside. Sprinkle the boats with a pinch of salt and pepper.

Par-bake the boats: Place zucchini cut-side up in the baking dish. Brush with a little oil. Bake for 10–12 minutes until just tender. This keeps them from getting soggy later.

Brown the beef: Heat a large skillet over medium-high. Add a drizzle of oil, then the ground beef. Break it up and cook until no longer pink. Drain excess fat if needed, leaving about a tablespoon for flavor.

Add aromatics: Stir in the diced onion and garlic. Cook 2–3 minutes until fragrant and softened.

Flavor the filling: Add chopped zucchini flesh, tomato paste, Worcestershire, smoked paprika, Italian seasoning, salt, and pepper. Stir well. Pour in the beef broth and simmer 3–4 minutes to thicken and concentrate flavor. Taste and adjust seasoning.

Cheese it up: Remove from heat and stir in half of the cheddar and half of the mozzarella until just melted and creamy.

Stuff the boats: Spoon the cheesy beef mixture into each par-baked zucchini boat, packing it in evenly.

Top and bake: Sprinkle the remaining cheeses over the boats. Bake 10–15 minutes, until cheese is melted and bubbly with light golden spots.

Finish and serve: Let rest 5 minutes. Garnish with chopped parsley or green onions. Add optional keto-friendly toppings like diced pickles or a drizzle of sugar-free ketchup and mustard for a true cheeseburger vibe.