Preheat your oven to 375°F (190°C).
Slice the top off the red bell pepper and carefully remove the seeds and internal membranes.
In a medium mixing bowl, combine the ground beef, cooked brown rice, garlic powder, dried oregano, half of the sea salt, half of the black pepper, and 2 tablespoons of the tomato puree.
Pack the beef and rice mixture tightly into the cavity of the bell pepper.
Place the stuffed pepper upright in a small baking dish, spoon the remaining tomato puree over the top, and cover the dish tightly with foil.
Bake for 35 to 40 minutes, or until the beef is cooked through and the pepper is tender.
While the pepper is roasting, thinly slice the cucumber and radishes into rounds.
In a small bowl, whisk together the olive oil, apple cider vinegar, dried dill, and the remaining sea salt and black pepper.
Toss the cucumber and radishes in the dressing and set aside to marinate in the refrigerator.
Serve the hot stuffed pepper immediately with the chilled cucumber salad on the side.