Prep the oven and pans: Heat the oven to 400°F (200°C). Line a large baking sheet with parchment or grease it lightly.

Hollow the zucchini: Trim the ends and slice zucchini lengthwise. Use a spoon to scoop out the centers, leaving about 1/4 inch shell. Chop about half of the scooped flesh to add to the filling; discard the rest or save for another use.

Season and pre-roast: Brush zucchini boats with olive oil, sprinkle with salt and pepper, and place cut-side up on the baking sheet. Roast for 10–12 minutes to soften while you make the filling.

Sauté aromatics: Warm 1 tablespoon olive oil in a large skillet over medium heat. Add onion and a pinch of salt; cook 3–4 minutes until translucent. Stir in garlic for 30 seconds.

Brown the beef: Add ground beef, breaking it up with a spatula. Cook until no longer pink, about 5–6 minutes. Drain excess fat if needed.

Build the taco base: Stir in taco seasoning and tomato paste; cook 30 seconds to bloom the spices. Add chopped zucchini flesh, crushed tomatoes, and broth. Simmer 3–4 minutes until thick and saucy.

Boost with mix-ins: Fold in black beans and corn. Taste and adjust seasoning with salt and pepper. The mixture should be well-seasoned since the zucchini is mild.

Fill the boats: Pull the zucchini from the oven. Spoon the beef mixture evenly into each boat, mounding slightly. Top with a generous sprinkle of shredded cheese.

Bake to finish: Return to the oven for 8–10 minutes, until cheese is melted and bubbly and zucchini is tender but not mushy.

Add fresh toppings: Let cool for a couple of minutes. Finish with cilantro, tomatoes, green onions, jalapeños, and a squeeze of lime. Add a dollop of Greek yogurt or sour cream and sliced avocado if you like.

Serve: Plate two boats per person for a hearty portion. Spoon any pan juices over the top for extra flavor.