Remove the crusts from the toast and cut into small triangles. Heat the fat and fry the toast in portions on both sides until golden brown. Wash the tomatoes and dab dry. Cut off a lid and carefully hollow out the tomatoes with a teaspoon.
Clean, wash and drain the rocket well. Puree half of the rocket and yoghurt in a tall container. Peel garlic and chop finely. Mix quark, garlic and pureed rocket yoghurt, season to taste with salt and pepper.
Sprinkle tomatoes from the inside with salt and fill the rocket quark into the tomatoes. Mix lemon juice, a little salt, pepper and sugar, add the oil. Arrange the remaining rocket, except for a few leaves for garnishing, on a plate and sprinkle with the vinaigrette.
Arrange the stuffed tomatoes and toast biscuits on top. Cut tomato lids into slices. Serve the stuffed tomatoes with the slices and the remaining rocket.