Boil the eggs hard for about 8 minutes, quench, peel and let them cool down. Clean and wash lettuce, tomatoes and radishes. Drain lettuce well and pluck into bite-sized pieces.
Cut tomatoes into eighths and radishes into quarters. Peel and halve the vegetable onion and cut into thin slices. Cut the eggs into eighths. Mix the vegetables and arrange in a salad bowl with the eggs. For the cress sauce, mix yoghurt and crème fraîche.
Season to taste with lemon juice, salt and pepper. Rinse cress, drain, cut off and, except for a teaspoon for garnishing, fold into the sauce. Pour the cress sauce over the salad and sprinkle with remaining cress.
Mix only before serving. This colourful salad tastes great with grilled meat, fish or sausages.