Cook the Rice: Combine the rinsed rice and 1½ cups (360 mL) water in a medium saucepan. Bring to a boil over medium-high heat.

Reduce the heat to low, cover, and simmer for approximately 15 minutes, or until the water has been absorbed and the rice is tender.

Remove the saucepan from the heat and let the rice stand, covered, for 5 minutes. Fluff with a fork and set aside.

Preheat the Oven and Prepare the Peppers: Preheat the oven to 375°F (190°C). Slice the bell peppers in half lengthwise, cutting through the stems if desired. Remove the seeds and white membranes while leaving the pepper walls intact.

Arrange the pepper halves cut-side up in a 9 × 13-inch baking dish.

Sauté the Onion: Heat the olive oil in a large skillet over medium heat.

Add the diced onion and cook for 3–4 minutes, stirring occasionally, until softened and slightly translucent.

Add the minced garlic and cook for another 30 seconds, stirring frequently until fragrant.

Brown the Ground Beef: Add the ground beef to the skillet with the onion and garlic.

Cook over medium-high heat for approximately 6–8 minutes, breaking the meat into small crumbles with a spatula.

Continue cooking until the beef is thoroughly browned and reaches an internal temperature of 160°F (71°C). Drain excess grease if necessary.

Season the Filling: Reduce the heat to medium: Add the tomato paste, Italian seasoning, paprika, kosher salt, and black pepper. Stir for approximately 1 minute, allowing the tomato paste to coat the beef and the spices to become fragrant.

The mixture should look evenly seasoned, with no large clumps of tomato paste.

Add the Tomatoes and Rice: Stir the diced tomatoes and their juices into the skillet.

Add ½ cup (120 mL) of the tomato sauce and the cooked rice. Mix gently until the rice and beef are evenly distributed.

Simmer for 2–3 minutes, allowing the rice to absorb some of the tomato juices. The mixture should be moist and cohesive, but not watery.

If the filling looks dry, add a tablespoon or two of water.

Prepare the Baking Dish: Pour the remaining ½ cup (120 mL) tomato sauce and ½ cup (120 mL) water into the bottom of the baking dish around the peppers.

Stir the liquids together gently without displacing the pepper halves.

This creates a moist cooking environment and helps prevent the peppers from sticking or drying out.

Stuff the Peppers: Spoon the beef and rice filling evenly into the six pepper halves.

Pack the filling gently without pressing it too tightly. Mound a little extra filling over the top of each pepper if necessary.

The filling should remain slightly loose so it heats evenly and maintains a pleasant texture.

Cover and Bake: Cover the baking dish tightly with aluminum foil. Bake at 375°F (190°C) for approximately 30–35 minutes, until the pepper walls begin to soften and can be pierced with a fork.

The peppers should still hold their shape rather than becoming mushy.

Add the Cheese: Carefully remove the foil from the baking dish, keeping your hands away from the escaping steam.

Divide the shredded mozzarella evenly among the six stuffed pepper halves.

Return the uncovered dish to the oven and bake for another 10–15 minutes, until the cheese is completely melted and beginning to develop light golden spots.

The peppers should be tender, and the filling should be hot throughout, reaching at least 165°F (74°C) in the center.

Rest and Garnish: Remove the baking dish from the oven and let the stuffed peppers rest for 5 minutes.

This allows the filling to settle and makes the peppers easier to transfer to individual plates.

Sprinkle with the optional chopped parsley and spoon a little of the warm tomato sauce from the baking dish around each serving.