Preheat your oven to 375°F (190°C). Slice the tops off the bell peppers and remove the seeds and membranes.
Place the peppers in a baking dish with a splash of water at the bottom, cover with foil, and pre-bake for 10 minutes to soften.
In a large skillet over medium heat, add the olive oil and sauté the diced onion and minced garlic until fragrant and translucent.
Add the ground turkey to the skillet, breaking it up with a spatula, and cook until browned and fully cooked through.
Stir in the turmeric, sea salt, and black pepper, ensuring the spices are evenly distributed.
Add the cooked brown rice, tomato sauce, and fresh spinach to the skillet, stirring until the spinach has wilted and the mixture is well combined.
Carefully remove the peppers from the oven and spoon the turkey and rice mixture into each pepper cavity, packing it down gently.
Return the stuffed peppers to the oven, uncovered, and bake for an additional 15-20 minutes until the peppers are tender and the tops are slightly golden.