Preheat the oven to 180C
Heat the olive oil in a pan with the garlic and add the Swiss chard and celeriac to saute for 10 minutes. Transfer the mixture to a baking dish with the lemon juice and seasoning and place in the oven for the total time of 25 minutes.
After the veggies have cooked for about 10 minutes, heat a seasoned grill pan to hot. Brush the eye fillet with olive oil and sear on all sides for 2 - 3 minutes. Place the meat on a baking tray to cook through for approx 10 minutes or until you like it done. Remove the meat from the oven and cover it with a piece of foil and leave to rest.
Roast the buckwheat in a small fry pan for about 4 minutes or until they darken slightly in colour.
Slice the eye fillet and serve alongside the vegetables and sprinkle the buckwheat over the top.