Cut off the stem and trim the bottoms of the zucchinis. Rinse them well and then cut them in half about 2,5 inch / 7cm each piece.
Using a knife and spoon or an apple corer remove most of the insides of the zucchini. This will leave you with a hollow zucchini, one end open, ready to be stuffed.
Prepare the filling in a bowl by mixing together the ground beef, red onion, parsley, dill, rice, and the 3 tablespoons of olive oil. Season the mixture with kosher salt and freshly ground pepper. Knead the mixture for 2 minutes.
Start filling the zucchinis by pressing the ground beef mixture into the hole with your finger. Press to make sure there aren't any air gaps left inside the zucchini.
Place the stuffed zucchinis tightly together, standing upright, in a pot or a baking pan.
Place 1/2 liter of water to boil. Add the beef bouillion cube to the water to dissolve.
Pour the beef broth into the pot or the baking pan with the stuffed zucchini.
Place the pot on medium to low heat and cook for about 45 minutes to 1 hour. Keep an eye on the pot so it does not go dry. Add hot water if needed. If baking in the oven, place into a baking pan tightly together and pour in the beef broth. Cover with aluminum foil and cook for 45 minutes or until tender, oven at 180 celsius or 360 farenheit.