Heat two tablespoons of olive oil in a large skillet over medium heat. Add the diced onion and sauté until softened and translucent. Then, stir in the chopped steak and cook until browned.

While the steak cooks, slice the bell peppers in half and remove the seeds. Rub a teaspoon of olive oil on both the inside and outside of each pepper.

Place the peppers, cut side down, in the air fryer tray or basket. Set the air fryer to 400°F and cook for 5 minutes, flipping the peppers halfway through (after about 2 minutes) to ensure even roasting.

Once roasted, remove the peppers and fill them with the steak and onion mixture. Top with a generous sprinkle of mozzarella cheese.

Return the stuffed peppers to the air fryer and cook at 400°F for another 3 minutes, or until the cheese is melted and bubbly.

Remove from the air fryer, plate, and enjoy!