Preheat your oven to 190°C (375°F). Slice off the tops of the peppers and carefully remove the seeds and membranes, creating a hollow shell. Place the peppers cut side up in a baking dish.
Finely chop the onion and mince the garlic. In a skillet, heat olive oil over medium heat until shimmering and fragrant, about 1 minute.
Add the chopped onion and garlic to the skillet. Cook, stirring occasionally, until softened and translucent, about 3-4 minutes, and the aroma becomes warm and inviting.
Add the cooked, crumbled turkey to the skillet. Stir well and cook for another 3-4 minutes until the mixture is heated through and slightly browned.
Stir in the tomato paste, chopped herbs, and season with salt and pepper. Cook for another minute until everything is combined and fragrant.
If using cooked grains, fold them into the mixture now, mixing thoroughly to distribute evenly.
Spoon the filling into each hollowed pepper, pressing down gently to compact the mixture. Fill all four peppers this way.
Sprinkle shredded cheese evenly over the top of each stuffed pepper. Place the dish in the oven and bake uncovered for 30-35 minutes, until the peppers are tender and slightly blistered, and the cheese is bubbly and golden.
Remove the dish from the oven and let sit for 5 minutes to allow the filling to set. Garnish with extra herbs if desired.
Serve the stuffed peppers warm, perhaps with a side salad or crusty bread, and enjoy their hearty, cheesy goodness.
