For the filling, dab the beetroot and cut it into small cubes (be careful, it stains strongly! Wear disposable gloves). Clean, wash, quarter and cut the bell peppers into thin strips. Peel and finely dice the onion.
Wash the chives, shake dry and cut into fine rolls. Crumble the feta.
Mix red beetroot with chives, oil, vinegar and onion. Season to taste with salt, pepper and a little sugar. Fold in feta cheese.
Warm the bread in the toaster, cut it open at the mark and fill it with the vegetables. Grill in a hot grill pan (or a coated pan) from both sides for 4-6 minutes, weighting down with a pot.
Serve immediately. Arugula salad is delicious with it.