Preheat oven to 160 °C.
Season the fillet.
Roll in the flour, then in the whisked eggs and finally in the ground biltong.
Oven-roast for 15 to 20 minutes until brown on the outside but still pink inside.
Take care not to overcook the meat.
Wrap the fillet in foil and leave in a warming drawer for 10 minutes.
Heat a griddle pan until smoking hot and char-grill the fillet.
Carve and serve with caramelised onions.
Stir-fry the onions in a little olive oil until soft.
Add the red wine vinegar, bay leaves, reduce the heat and simmer until the liquid has evaporated.
Add the red wine and reduce until the mixture is syrupy.