Purée the olives, except for a few for garnishing, and oil with a blender to a homogenous mass. Season with salt and pepper. Toast slices of toast in a toaster and brush with butter. Spread olive paste in portions on the toasts.
Wash the tomatoes, cut them in half and put them on the toast. Slice the parmesan and sprinkle over the toasts. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for about 4 minutes.
Garnish with parsley and olives.