Kosher salt and freshly ground black pepper, to taste
1 cup mozzarella cheese, grated
Preheat oven to 350°F and set aside a 9x13-inch baking dish.
Cut the tops off of the peppers and remove the seeds.
In a large skillet, heat the olive oil over medium-high heat. Add the red onion and cook until starting to soften, about 3 minutes. Add ham and cook until edges brown, about 2 minutes. Add garlic and cook 1 minute more.
Add rice and teriyaki sauce and stir to combine. Season to taste with salt and pepper.
Remove from heat, and stir in pineapple and green onion. (Drain pineapple if using canned.)
Spoon mixture into bell peppers, top with cheese, and arrange in baking dish.
Pour 1/2 cup water into the bottom of the baking dish, cover tightly with foil and bake until peppers are tender and filling is heated through, 30 minutes. Remove foil and bake until cheese is lightly browned, 5 minutes more.