Preheat the oven to 190 degrees. Wash the large red bell pepper, cut off the top and carefully remove the seed pods and seeds. Finely mince the quarter onion and chop or press the garlic clove.
Heat a frying pan and sauté the minced onion and garlic in it. Add the lean ground beef and half a teaspoon of oregano. Cook the meat on medium-high heat until crumbly and cooked through. Stir the ten grams of pine nuts briefly through the meat mixture and remove the pan from the heat.
Scoop the warm meat mixture into the hollowed out bell pepper. Press the filling down lightly so everything fits in. Place the stuffed bell pepper upright in a baking dish and place this in the preheated oven. Bake for twenty to twenty-five minutes until the pepper is cooked and soft.
Remove the baking dish from the oven. Spread a handful of arugula over a plate and place the warm stuffed bell pepper in the middle to serve immediately.