Clean and wash the cucumber and cut into thin slices. Radishes clean, wash and cut into slices. Clean and wash lamb's lettuce thoroughly and let it drip off in a sieve. For the dressing, stir yoghurt with lemon juice until smooth, season with salt and pepper
Toast the sandwich slices one after the other in the toaster. Spread the toast slices with 1/2 tbsp. tomato paste each. Cover 4 toast slices with lamb's lettuce, cucumber and radish.
Spread yoghurt dressing on top. Cover with remaining toast slices. Cut the sandwich diagonally, arrange on plates and sprinkle with black pepper from the mill as desired. Serve with a glass of almond drink