Preheat your oven to 360°F (180°C) and line a baking sheet with parchment paper.

Wash the zucchinis and slice them in half lengthwise, then scoop out the seeds and flesh.

In a skillet, heat olive oil and sauté the chopped onion for about 5-7 minutes.

Add ground beef to the skillet and cook for 8-10 minutes until browned.

Stir in tomato paste, Italian seasoning, garlic powder, salt and pepper, and cook for 2 more minutes.

Pour in the tomato sauce and simmer over low heat for about 15 minutes.

Fill the zucchini halves with the beef mixture, leaving some space at the top.

Sprinkle shredded mozzarella cheese on top of each filled zucchini.

Bake in the oven for about 20 minutes until the zucchinis are tender and cheese is melted.